Abstract
The paper presents the method for assessment the population that is not counted by the official census. The capture and re-capture method for wildlife population assessment is applied. The method is based on marking of the individuals in the sample, and counting the quantity of the marked individuals in the second sample. The ratio is used to assess the quantity of the group in the entire population. The limitations of the theory are discussed, and they are related to the choice of the region for the survey and sampling due to non-homogeneity of the regions. Basing on the US census methodology, migrants (assumed de-facto residents) are used as the group not counted by the official census. The theory is applied for the December 2015 population for the hypothetical samples (size about 1000), the wildlife population parameters are calculated, and the ratio of the uncounted population is assessed as 0.00074% for this group.
The statistical assessments of the population is important for understanding of the demographic and economic state of the country. Basing on the population data, the government plans the medical and social programs. The organization responsible for the population evaluation is the US Census bureau. It estimates the US population on a monthly basis. Thus, in December 2015, the resident population estimate was 325,032,763 (United States Census Bureau, 2015). However, some people remain beyond the official statistics. Thus, the question:
“What is the population of the United States — including those who are not counted in the official census?” arises. The reply requires application of the specific methodology, and determination of the groups who are not included in the census data.
The number of people who are not counted in the official statistics can be estimated using capture and recapture method commonly used in biology for wildlife population assessment. For this, two samples of relatively great size are taken. In the first samples, the species of interest are specifically marked (M represents the number of the marked) and then released. Then, the second sample (recapture) is taken with the size n. In this sample, the number of the marked species (R) is calculated. Then, the ratio (R / n) of the marked in the second sample is calculated. The ratio R/n is assumed to be the same as in the whole population. Therefore, the number in the whole population can be counted as M / (R / n) (Zeng, 2009).
The advantages of the methodology is its relative simplicity and inexpensiveness. The disadvantages are related to the limitations of the wildlife method. The population is assumed to be closed, e.g. the individuals are limited in the migration ability. In addition, the wildlife model suggests that the environmental conditions are equally favorable for the individuals. When human population is concerned, the regions are definitely non-homogenous, i.e. there are regions that are more favorable for the illegal migrants. These are the regions with the numerous low-paid job opportunities. Therefore, this factor has to be considered when the region for the sampling is chosen.
Basing on methodology of the census, the population calculates:
Population Base + Birth – Death + Migration = Population Estimate
The important component of the formula is migration component. In the USA, there are people who de-facto are residents of the USA, but are not counted in the census estimated. These illegal immigrants stay in the country for the long period. Therefore, the wildlife method can be applied.
Thus, the sample should be taken with the significant number, for example 1000 people. To answer the question about the population estimate, the survey should either have the full name of the representative, or the question that would clearly mark the participation in both samples (this is the analogue of the specific marking in wildlife population). These people should be questioned to determine if they are residents or migrant who live in the USA for the extended period. Then, the number of the individuals should be recorded. As the second sample survey is collected, the number of the marked individuals is counted, and the ratio calculated. Thus, these data are enough to assess the uncounted population.
Suppose that this number of the marked individuals is M = 126. The second sample size is n = 862, and the number of the recaptured marked individuals is R = 45. The numbers and the calculation process are presented in Table 1.
Hence, the estimated number of de-facto residents that are not counted in the official census is 2414, and this is 0.00074%. The same way, the unregistered birth can be assessed, as well as any other population groups left beyond the statistics.
In conclusion, the application of the wildlife assessment methodology allows estimation of the individuals quantity that are not counted as US population. The accurate assessment can be performed if the wildlife theory limitation is considered.
References
United States Census Bureau. (2015, July). Methodology for the United States population estimates: Vintage 2015. United States Census Bureau. Retrieved from US Census Bureau website http://www.census.gov/popest/methodology/2015-natstcopr-meth.pdf.
United States Census Bureau. (2016). Retrieved from US Census Bureau website http://www.census.gov.
Zeng, Y. (2009). Demography. Oxford: EOLSS.
