- Open Access
Evaluation of geoimputation strategies in a large case study
© The Author(s) 2018
- Received: 27 March 2018
- Accepted: 25 July 2018
- Published: 31 July 2018
Health data usually has missing or incomplete location information, which impacts the quality of research. Geoimputation methods are used by health professionals to increase the spatial resolution of address information for more accurate analyses. The objective of this study was to evaluate geo-imputation methods with respect to the demographic and spatial characteristics of the data.
We evaluated four geoimputation methods for increasing spatial resolution of records with known locational information at a coarse level. In order to test and rigorously evaluate two stochastic and two deterministic strategies, we used the Texas Sex Offender registry database with over 50,000 records with known demographic and coordinate information. We reduced the spatial resolution of each record to a census block group and attempted to recover coordinate information using the four strategies. We rigorously evaluated the results in terms of the error distance between the original coordinates and recovered coordinates by studying the results by demographic sub groups and the characteristics of the underlying geography.
We observed that in estimating the actual location of a case, the weighted mean method is the most superior for each demographic group followed by the maximum imputation centroid, the random point in matching sub-geographies and the random point in all sub-geographies methods. Higher accuracies were observed for minority populations because minorities tend to cluster in certain neighborhoods, which makes it easier to impute their location. Results are greatly affected by the population density of the underlying geographies. We observed high accuracies in high population density areas, which often exist within smaller census blocks, which makes the search space smaller. Similarly, mapping geoimputation accuracies in a spatially explicit manner reveals that metropolitan areas yield higher accuracy results.
Based on gains in standard error, reduction in mean error and validation results, we conclude that characteristics of the estimated records such as the demographic profile and population density information provide a measure of certainty of geographic imputation.
- Address data
- Coarse resolution
- Census data
Spatial epidemiology is the study of geographic variation of diseases. Locational accuracy is essential in geographical studies including epidemiological studies where the locational characteristics and behaviors of the patient are key to understand the underlying risk factors to inform policymaking. For example, underlying spatial factors such as environmental exposures have been linked to cancer including, asbestos exposure and mesothelioma, polychlorinated biphenyls (PCBs) and melanoma, aflatoxin and liver cancer, benzene and acute myeloid leukemia, tobacco and multiple cancers, and air pollution and lung cancer [1–8]. Besides cancer, environmental exposures are also associated with other diseases, for example, air pollution has been linked with respiratory disease, cardiovascular disease, and reproductive health [9–12]. Spatial epidemiology and geographic information systems (GIS) have also been applied to non-environmental health issues, including understanding the built environment , health planning , and crime data .
While high quality scholarly research requires reliable locational information of exposures and outcomes, the level of spatial detail available to health researchers is often not sufficiently fine resolution. This is for two main reasons: (a) while health information is exceedingly valuable, it is protected by federal law and thus it is imperative to protect the privacy of individuals; and (b) information is often only collected or made available at a lower resolution, such as the zip code or county level. For health data, the exact geographic coordinates of participants are often not available without a data request and several levels of approval to ensure the confidentiality of participants is maintained. Failure to accurately and precisely capture geographic information may lead to incorrect findings and conclusions, including an overestimation of the true association  or imprecise estimates [17, 18]. Researchers often work with data with coarse resolution (e.g. when the complete street address is missing and only the ZIP code is available), resulting in omitted records and potentially creating biases due to misclassification . Geocoding to ZIP code area centroids, a common practice in health research, often falsely indicates clustering at the centroid [20, 21], especially so in rural communities .
In order to rectify issues associated with imprecise spatial data, several spatially informed geo-imputation methods have been developed to increase the spatial resolution. They are similar to disaggregation methods , which interpolate data at smaller units using the spatial distribution of ancillary data.
Geo-imputation strategies can generally be divided into stochastic and deterministic methods. One method for stochastic geo-imputation is the use of the cumulative distribution function to randomly assign a case to a locale [23–25]. A variety of this method uses a variable such as population to construct the probability of a locale being chosen . Deterministic methods assign cases to locales deterministically, based on a set of rules, such as the geographically weighted mean of locales, or the centroid of the locale  that is the best fit. A mixture of the two can be used as well by selecting a random point within a deterministically chosen locale. Although the literature on the use of imputation for missing address information is sparse, authors have used both stochastic and deterministic methods, including alone and in combination [23, 27–32]. For example, Curriero et al.  found that misclassification in assignment of correct census tract was reduced most using deterministic geoimputation weighted by specific ethnicity/age population in comparison to a stochastic method and other types of deterministic methods. Walter and Rose  devised a stochastic method called random property allocation, which randomly assigns each case with incomplete address information to an address that was previously geocoded within the corresponding geographical unit, where each address has equal probability. They compared this method to one stochastic and three deterministic geo-imputation methods, which assign incomplete addresses to geographic centroids, population weighed centroids, areal proportion using random function and areal proportion using deterministic function, similar to the methods mentioned before. The authors observed that while all geo-imputation methods performed well, the random allocation method was the least prone to bias, as centroid based methods can create artificial clustering and bias.
The accuracy of geographic imputation methods is typically assessed by comparing the results from several methods. The results can be assessed based on: (a) the ratio of correct estimates, e.g. the number of times a case was assigned to the correct geographical unit; or (b) based on the distance between the predicted and known coordinates. Theoretically, when ground truth data is not available, it is not possible to evaluate the accuracy of the results. In this study, we are not focused on missing spatial data but rather our focus is on the application of geo-imputation methods to improve the spatial accuracy of spatial data by estimating higher resolution locations of events or persons based on known lower resolution spatial information (such as ZIP code) and supporting information (such as demographic characteristics). In this study, we apply four geo-imputation methods, including both stochastic and deterministic, to impute coordinate level information followed by an evaluation of the performance of the geo-imputation methods using the demographic sub groups and the characteristics of the underlying geography.
Demographic summary of the Texas Sex Offender Registry 2017 used in the study
Age < 20
20 ≤ Age < 50
50 ≤ Age < 65
65 ≤ Age < 85
Age ≥ 85
The sex offender registration laws in Texas went into effect on September 1, 1991. Among other information, The Texas Sex Offender Registration Program requires offenders to submit full name, date of birth, sex, race, height, weight, eye color, hair color, social security number, driver’s license number, shoe size, home address or a detailed description of each geographical location at which the person resides or intends to reside.
Adult sex offenders must register either for life or for 10 years depending on certain conditions.
Registered offenders must report address changes.
Sex offenders may be prohibited from living in child safety zones defined by laws and city ordinances, as well as campuses of higher education.
This information means the data is not collected at specified, regular intervals, but whenever there is a new entry and as soon as possible after an address change. Demographic data for the population includes age, gender and ethnicity information from 2010 Census Summary File 1 (SF1)  at census block level, which is the target resolution to assign our data. The SF1 data includes nine ethnic groups and 23 population ranges for both males and females, resulting in 414 possible demographic combinations. Additional file 1: Tables S1 and S2 list the complete list of race and age groups in the Census data.
This demographic data was merged and joined to the census block shapefile with NAD 1983 Texas Centric Mapping System Albers projection. There are 914,231 census blocks in the State of Texas.
Obtain census block information using GIS.
Obtain census block group (to reduce data quality for the purposes of validating imputation).
Impute X, Y coordinates based on census blocks with census information for each method.
Calculate error distance for each strategy.
Thus, we first reduce the data quality of each X, Y record by selecting its block group in order to make the data comparable to the more coarse spatial data quality (steps a and b). In the next step (c), we attempt to improve the spatial data quality by correctly assigning each X, Y record to the correct census block. In the last step (d) we evaluate our results by calculating the distance between the point assigned to the census block, and the original X, Y record.
The chosen geo-imputation methods were derived from the literature, in order to assign a non-geocoded record with census block group information to (a) a random point within the entire census block group; (b) a random point within the extents of matching blocks; (c) the centroid of census block with the highest weight; and (d) the weighted centroid of the matching census blocks. We chose the following methods which are either stochastic or deterministic methods identified from the literature [23, 28–30].
Imputation Strategy #1 and #2
The following two imputation methods generate geoimputed results based on a complete random spatial function. These methods provide a basis to test the relative usefulness of the deterministic methods (3 and 4) that rely on the underlying demographic characteristics.
Strategy #1, random in Block Group, assigns the record to a random point within the entire block group as used in Henry and Boscoe . Strategy #2, random in Matching blocks, randomly assigns a random point only within blocks that have matching demographic population to the individual record.
Imputation Strategy #3
This method can be prone to generating artificial clusters , as all imputed coordinates from a particular geographical unit (which is chosen as it has the highest weight) will be identical.
Imputation Strategy #4
This strategy assigns the record to the weighted centroid of the matching census blocks using the mean center of the available population similar to the approach used by Walter and Rose . However, we matched demographics to target smaller population (as in Eq. 1) rather than the general population only. This strategy requires first calculating the centroid of each census block, and then calculating one final centroid based on their imputation weights calculated according to Eq. 1. In this approach, the weight of each block is calculated using one of the 414 combinations based on the case’s gender, age, and race within the block group to which it belongs. This method can be compared to the previous imputation strategy, as both methods make use of the block weights. The difference is that this method results in an estimation built by the entire set of candidate geographies based on how likely they are to contain a specific case. Also, unlike the previous imputation strategy, this strategy is not prone to artificial clustering since it is nearly impossible to generate the same weighted mean center. Two imputations would overlap only if they are in the same census block group with identical demographic characteristics.
Evaluation of the accuracy of the imputation strategies
We evaluate the imputation strategies described above by comparing the original coordinates with geo-imputed coordinates using all records. We calculated the distance between the imputed location and the actual location (accuracy), stratified by age groups and ethnicities since certain demographic groups may cluster spatially, while others distribute more uniformly. Thus, high accuracy location data can be deduced when the target demographics are very particular and only exist in one or a few candidate geographies. We also evaluated the results by population density, as we expected the results to be more accurate when the underlying geographical unit is smaller.
We developed box and whisker plots to display the accuracy of each geo-imputation method and underlying factors, validated the stochastic methods using multiple imputation, assess the sensitivity of results based on the administrative boundary type, and map the geographic inaccuracy. We expected to observe differences in geographical patterns of imputation accuracy across space (e.g. particular neighborhoods, rural areas, etc.).
We geoimputed 96.7% of records (n = 50,494) by all four strategies; the other 1734 records could not be geoimputed by Strategies #3 and #4 as they did not have any matching population in the searched census block group. This is potentially due to the difference in dates of data collection (Texas Sexual Offender Registry date of offense vs. US Census data restricted to 2010, the date census data was collected) combined with addresses change, or inaccuracies in data collection. In addition, many factors could account for this small number of records that could not be imputed including known racial misclassification issues [35, 36].
Accuracy by imputation strategy and demographic group
Figure 3 provides the mean error distance between the imputed points and the actual points broken down by age group and geo-imputation method (see Additional file 1: Table S3 for information on gender). These results also indicate that in estimating the actual location of a case, the weighted mean method (Strategy #4) is almost always the most superior for each demographic group followed by the maximum imputation centroid (Strategy #3), the random point in matching sub-geographies (Strategy #2) and the random point in all sub-geographies methods (Strategy #1). The only exception is the 65–85-year-old Asian subgroup, which has only 5 cases, as well as the American Indian/Alaska Native (AI/AN) group as a whole.
Accuracy by imputation strategy and population density
Certainly, it makes sense to expect high accuracies in areas with high population density, these areas are typically identified by smaller census blocks and decreasing the search space. Error results range from 48,300 m by a random estimate to only 58 m by the weighted mean estimate in our population density analysis. We observed that at the low end of the population density (0.01–0.1 people/km2), the performance of methods #1, #2, and #3 were not significantly different while method #4 performs significantly better than the first three methods. At the high end of the population density (10,000–35,000 people/km2) the methods fall into two groups with methods #3 and #4 performing better than methods #1 and #2 (Fig. 5).
To evaluate the sensitivity with respect to different spatial units, we used the smaller sample set and reduced the spatial resolution first to census tracts and then to counties. We then conducted the identical analyses with all four strategies using these spatial units.
Accuracy across geography
We developed a methodological approach to evaluate various geoimputation methods with a large data set with complete, known, addresses and demographic information. Through rigorously evaluating the results stratified by demographic sub groups, population density, and geography, we have contributed additional knowledge to the field [23–25, 30].
This approach can be applied in contexts with missing addresses to increase the spatial resolution of the existing information. In such application, limitations and potential uncertainties of the geoimputation can be deduced from the size and population density of the underlying geography, as well as particular characteristics of the demographical profile of the particular record. We found that strategy #4, the Weighted Mean method, performed the best overall as in Curriero et al. , and in almost all sub evaluation criteria. This also supports Henry and Boscoe’s  stochastic method weighted by race and ethnicity population as opposed to a random point or a geographic centroid. As in Henry and Boscoe’s  study, we presented results by ethnicity, age and population density (also as in Walter and Rose  who evaluated them based on Metropolitan vs. Non-Metropolitan areas), but with further detail. Similar to Hibbert et al. , which report results by geography (i.e. four states), we report the results across the space. As in JD Hibbert et al.  and FC Curriero et al. , we also conducted multiple imputation of a sample set to validate our results. In addition, we conducted sensitivity analyses using two coarser spatial units of census tracts and counties. All the reviewed studies evaluated results based on assignment to correct unit, while we reported the results based on distance between predicted point and the actual point. We argue that correct assignment probability depends on the number of high resolution units in the search space, and therefore reporting the error distance can be viewed as an alternative way to evaluate different methods.
The range of error based on the demographic characteristics and population density is instructive for researchers working with limited locational information. For example, for some exposures of interest, sub kilometer gains in accuracy in urban core areas may not be very significant on epidemiological associations. On the other hand, the accuracy gains based on certain demographic groups or population densities (such as rural areas) may provide required level of accuracy to establish such associations.
We use demographic data from the Census Bureau from 2010. If the demographics of the case’s location changed from the time of the decennial census, our error estimates would be impacted. Similarly, the individuals on the sex offender registry could have moved, and would report a different address to the registry than the address reported at the census. This might explain some of the 1734 records that could not be geoimputed by Strategies #3 and #4.
Potential data collection inaccuracies could also result in misclassification of race/ethnicity. For example, there are 13,336 records reporting a white race with unknown ethnicity, which we corresponded as white race in the Census data. We also corresponded the 26,135 records with white race with Hispanic ethnicity to the Hispanic or Latino race category in the Census data (Additional file 1: Table S1). While we assumed that other attributes are collected correctly, while there is no feasible way to validate them.
While the sexual offender dataset is very large, it may still not be representative of the general population in terms of demographics as well as living preferences/limitations. For example, only 2.5% of the records belong to females. This is not comparable to many other health outcomes where these methods may be applied, including cancer rates among men and women, which ranges between 7:4 and 3:2 . Additionally, we assume that the individuals in this database are randomly dispersed throughout the community, which is unlikely because of their status as a sexual offender.
Many publicly-available datasets, including state-level cancer incidence and mortality data and the Surveillance Epidemiology and End Results program data are generally available at the county level, prohibiting detailed analysis with complete address information due to privacy and confidentiality concerns. Although additional validation in other datasets that include both genders are needed, these methods are generalizable to other publicly-available datasets. Future studies may apply these methods to other types of health data with missing complete address information and to data sources that lack certain demographic information, at the expense of generating additional uncertainty.
Future studies should consider conducting geoimputation at other geographic levels, including ZIP code level information or applying a method based on cumulative random function, which would assign cases to finer spatial units randomly based on weights. Theoretically the deterministic imputation methods used in this study can be further improved by utilizing additional data, such as income, education etc., if available. These methods can be further enhanced by additional GIS or Remote Sensing data to exclude areas that do not contain residences. For example, we could eliminate areas without any residential buildings with a combination of GIS (zoning) and RS (impervious surface) data and methods.
Based on gains in standard error, reduction in mean error and validation results, we conclude that methods #3 and #4, Maximum Imputation and Weighted Mean methods were preferable in this study when no fine level spatial information is available, though this should be replicated in a population that is more randomly dispersed. We conclude that characteristics of the estimated records such as the demographic profile and population density information impact accuracy of results. In the absence of ground truthing information, such variables can provide accuracy information using the error ranges provided in this study.
ND obtained the registry data, collected census and geographical data, developed and ran the code for geo-imputation, conducted the statistical analyses and wrote the first draft. AEJ, JEB and KMB provided guidance in interpretation of results. All authors helped to draft the manuscript. All authors read and approved the final manuscript.
The authors declare that they have no competing interests.
Availability of data and materials
Data used in this study including Texas Sex Offender Registry data, Census Bureau SF1 data, and TIGER files are publicly available.
Consent for publication
Ethics approval and consent to participate
It was determined by the Institutional Review Board for the Protection of Human Subjects, University of Oklahoma that this research did not meet the criteria for human subject’s research. Therefore, IRB approval was not necessary.
This work was supported by The Oklahoma Center for the Advancement of Science and Technology, Grant No. HR16-048.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
- Berwick M, Buller DB, Cust A, Gallagher R, Lee TK, Meyskens F, Pandey S, Thomas NE, Veierød MB, Ward S. Melanoma epidemiology and prevention. In: Kaufman LH, Mehnert MJ, editors. Melanoma. Cham: Springer; 2016. p. 17–49.View ArticleGoogle Scholar
- Saracci R, Wild CP. International Agency for Research on Cancer: the first 50 years, 1965–2015. Lyon: International Agency for Research on Cancer; 2015 (distributed by World Health Organization Press).Google Scholar
- Steenland K, Hein MJ, Cassinelli RT, Prince MM, Nilsen NB, Whelan EA, Waters MA, Ruder AM, Schnorr TM. Polychlorinated biphenyls and neurodegenerative disease mortality in an occupational cohort. Epidemiology. 2006;17(1):8–13.View ArticlePubMedGoogle Scholar
- Straif K, Cohen A. International Agency for Research on Cancer: air pollution and cancer. Lyon: International Agency for Research on Cancer; 2013 (distributed by World Health Organization Press).Google Scholar
- IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. Arsenic, metals, fibres and dusts: a review of human carcinogens. In: IARC monographs on the evaluation of carcinogenic risks to humans, vol. 100C. Lyon: International Agency on Cancer, World Health Organization; 2012.Google Scholar
- International Agency for Research and Cancer. IARC monographs on the evaluation of carcinogenic risks to humans: preamble. Lyon: International Agency for Research and Cancer; 2015.Google Scholar
- Grosse Y, Loomis D, Guyton KZ, El Ghissassi F, Bouvard V, Benbrahim-Tallaa L, Mattock H, Straif K. Carcinogenicity of some industrial chemicals. Lancet Oncol. 2016;17:419–20.View ArticlePubMedGoogle Scholar
- Benbrahim-Tallaa L, Baan RA, Grosse Y, Lauby-Secretan B, El Ghissassi F, Bouvard V, Guha N, Loomis D, Straif K. Carcinogenicity of diesel-engine and gasoline-engine exhausts and some nitroarenes. Lancet Oncology. 2012;13(7):663–4.View ArticlePubMedGoogle Scholar
- Nardone A, Neophytou AM, Balmes J, Thakur N. Ambient air pollution and asthma-related outcomes in children of color of the USA: a scoping review of literature published between 2013 and 2017. Current Allergy and Asthma Reports. 2018;18(5):29.View ArticlePubMedGoogle Scholar
- Vidale S, Campana C. Ambient air pollution and cardiovascular diseases: from bench to bedside. European Journal of Preventive Cardiology. 2018;25(8):818–25.View ArticlePubMedGoogle Scholar
- Carre J, Gatimel N, Moreau J, Parinaud J, Leandri R. Does air pollution play a role in infertility? A systematic review. Environ Health. 2017;16(1):82.View ArticlePubMedPubMed CentralGoogle Scholar
- Checa Vizcaino MA, Gonzalez-Comadran M, Jacquemin B. Outdoor air pollution and human infertility: a systematic review. Fertil Steril. 2016;106(4):897–904.e891.View ArticlePubMedGoogle Scholar
- Wang X, Khattak A, Chen J. Accuracy of geoimputation. Transportation Research Record: Journal of the Transportation Research Board. 2013;2382:10–9.View ArticleGoogle Scholar
- Nykiforuk CIJ, Flaman LM. Geographic information systems (GIS) for health promotion and public health: a review. Health Promotion Practice. 2009;12(1):63–73.View ArticlePubMedGoogle Scholar
- Kounadi O, Ristea A, Leitner M, Langford C. Population at risk: using areal interpolation and Twitter messages to create population models for burglaries and robberies. Cartography and Geographic Information Science. 2018;45(3):205–20.View ArticlePubMedGoogle Scholar
- Jacquemin B, Lepeule J, Boudier A, Arnould C. Impact of the geocoding technique on the associations between long-term exposure to urban air pollution and lung function. Environ Health Perspect. 2013;1054:1–93.Google Scholar
- Mazumdar S, Rushton G, Smith BJ, Zimmerman DL, Donham KJ. Geocoding accuracy and the recovery of relationships between environmental exposures and health. International Journal of Health Geographics. 2008;7:13.View ArticlePubMedPubMed CentralGoogle Scholar
- Zandbergen PA, Green JW. Error and bias in determining exposure potential of children at school locations using proximity-based GIS techniques. Environ Health Perspect. 2007;115:1363–70.View ArticlePubMedPubMed CentralGoogle Scholar
- Hurley SE, Saunders TM, Nivas R, Hertz A, Reynolds P. Post office box addresses: a challenge for geographic information system-based studies. Epidemiology. 2003;14(4):386–91.PubMedGoogle Scholar
- Zimmerman DL, Fang X, Mazumdar S. Spatial clustering of the failure to geocode and its implications for the detection of disease clustering. Stat Med. 2008;27:4254–66.View ArticlePubMedGoogle Scholar
- Krieger N, Waterman P, Chen JT, Soobader MJ, Subramanian SV, Carson R. Zip code caveat: bias due to spatiotemporal mismatches between zip codes and US census-defined geographic areas—the public health disparities geocoding project. Am J Public Health. 2002;92(7):1100–2.View ArticlePubMedPubMed CentralGoogle Scholar
- Kravets N, Hadden WC. The accuracy of address coding and the effects of coding errors. Health and Place. 2007;13:293–8.View ArticlePubMedGoogle Scholar
- Curriero FC, Kulldorff M, Boscoe FP, Klassen AC. Using imputation to provide location information for nongeocoded addresses. PLoS ONE. 2010;5(2):e8998.View ArticlePubMedPubMed CentralGoogle Scholar
- Henry KA, Boscoe FP. Estimating the accuracy of geographical imputation. Int J Health Geogr. 2008;7:3.View ArticlePubMedPubMed CentralGoogle Scholar
- Hibbert JD, Liese AD, Lawson A, Porter DE, Puett RC, Standiford D, Liu L, Dabelea D. Evaluating geographic imputation approaches for zip code level data: an application to a study of pediatric diabetes. Int J Health Geogr. 2009;8:54.View ArticlePubMedPubMed CentralGoogle Scholar
- Jones SG, Ashby AJ, Momin SR, Naidoo A. Spatial implications associated with using Euclidean distance measurements and geographic centroid imputation in health care research. Health Serv Res. 2010;45(1):316–27.View ArticlePubMedPubMed CentralGoogle Scholar
- Baker J, White N, Mengersen K. Missing in space: an evaluation of imputation methods for missing data in spatial analysis of risk factors for type II diabetes. International Journal of Health Geographics. 2014;13(1):47.View ArticlePubMedPubMed CentralGoogle Scholar
- Henry KA, Boscoe FP. Estimating the accuracy of geographical imputation. International Journal of Health Geographics. 2008;7:3.View ArticlePubMedPubMed CentralGoogle Scholar
- Hibbert JD, Liese AD, Lawson A, Porter DE, Puett RC, Standiford D, Liu L, Dabelea D. Evaluating geographic imputation approaches for zip code level data: an application to a study of pediatric diabetes. International Journal of Health Geographics. 2009;8:54.View ArticlePubMedPubMed CentralGoogle Scholar
- Walter SR, Rose N. Random property allocation: a novel geographic imputation procedure based on a complete geocoded address file. Spatial and spatio-temporal epidemiology. 2013;6:7–16.View ArticlePubMedGoogle Scholar
- Seon-Ju Y, Shon C. How can we assess the effects of urban environment on obesity using aggregated data? [abstract]. Paper presented at international society for disease surveillance annual conference proceedings 2018. Orlando, FL. https://doi.org/10.5210/ojphi.v10i1.8329.
- Wang X, Khattak A, Chen J. Accuracy of geoimputation: an approach to capture microenvironment. Transp Res Rec. 2013;2382(1):10–9.View ArticleGoogle Scholar
- Texas Public Sex Offender Registry. https://records.txdps.state.tx.us/sexoffender/. Accessed 28 Aug 2017.
- U.S. Census Bureau. 2010 Census Summary File 1 Texas. 2011.Google Scholar
- Strmic-Pawl HV, Jackson BA, Garner S. Race counts: racial and ethnic data on the US census and the implications for tracking inequality. Sociology of Race and Ethnicity. 2018;4(1):1–13.View ArticleGoogle Scholar
- Terry RL, Schwede L, King R, Martinez M, Childs JH. Exploring inconsistent counts of racial/ethnic minorities in a 2010 census ethnographic evaluation. Bulletin of Sociological Methodology. 2017;135(1):32–49.View ArticleGoogle Scholar
- Cancer Rates by Race/Ethnicity and Sex. https://www.cdc.gov/cancer/dcpc/data/race.htm. Accessed 22 Mar 2018.