New techniques in small area population estimates by demographic characteristics

The increasing demand for small area population estimates calls for both innovative ways of using existing data and new techniques suitable for small area estimates. This paper explores the methods for population estimates by age, sex, race, and Hispanic origin at the census tract level for Multnomah County, Oregon. New techniques include employing building permits to indirectly estimate migration and examining the changes in age/sex structure using the American Community Survey (ACS). A practical method for bridging the race categories is also developed. Finally, the paper discusses some reflections on small area estimates and the potentials of using ACS to track the changes of the demographic characteristics for the sub-county level.     

Note on the accuracy of local population estimates

Mr. Silcock's article will be of interest to all concerned with local population data. It may be useful to supplement it by a brief account of the fuller examination of the local population estimates made in 1951 by the General Register Office, since this covered all 1472 administrative areas in England and Wales and could be made in more detail than was possible for a private investigator.

Any census, of course, provides information not available, at least in such detail, at other times or from other sources, and also serves as a base from which estimates for succeeding years can be derived. In addition, however, the General Register Office takes the opportunity of a census to try and assess the accuracy of the various types of current population estimates made by the Department. In the case of local administrative areas the comparison of actual and expected populations made after the 1931 Census is discussed in the Text Volume of the Registrar General's Statistical Review for 1930 (pages 100-102).     

The estimation of small town aboriginal population change

In forecasting the effects of large-scale development projects on small town communities there is a need to consider the Aboriginal component of the population separately, not least to ensure the success of government policies regarding social welfare and Aboriginal advancement. This paper outlines some of the methodological and conceptual issues associated with the estimation of Aboriginal population change in the rapidly growing town of Katherine, in the Northern Territory, and reports on selected social and economic impacts of recent in-migration. Attention is drawn to the inappropriateness ofde facto population figures as a basis for planning and the need to estimate service requirements in the context of high population mobility.     

人口流动对农村人口老龄化的影响研究——基于“五普”和“六普”数据分析

我国农村人口老龄化程度和提高的速度全面超越了城市,这与当前的人口城市化进程密切相关。人口流动的年龄选择性,使得农村流出人口平均年龄和老年人口比例都远低于农村人口整体水平。流动人口内部在不断地"更新",年轻的流动人口不断替代年老的流动人口,从而保持较年轻的年龄结构,这种人口流动的年龄选择性加速了农村人口老龄化。通过人口老龄化模型的进一步分析发现,在2000～2010年间,农村人口自然老化速度基本保持稳定。而随着农村流动人口的增加,其对农村人口老龄化速度的影响从2000～2005年间的0.031岁/年增加到2006～2010年间的0.07岁/年;农村流出人口对农村人口平均年龄增加的贡献也从8.04%上升到16.91%,人口流动已成为农村人口老龄化的重要推动力。从人口流动的角度,需要关注农村留守老人的照料问题,进一步完善农村社会保障体系以及解决如何让流动人口在城市沉淀下来等问题。     

Report on a multiple regression method for making population estimates

A new method of making population estimates is introduced and contrasted to the standard ratio-correlation method. The new method, called the “difference-correlation method,” produced population estimates for the counties of Michigan which had a smaller mean percentage error than estimates produced by the ratio-correlation method. The differences of proportions which are used in the difference-correlation method will always have means of zero, while the ratios used in the ratio-correlation method have means which vary. Higher intercorrelations among the variables and increased temporal stability of the intercorrelations are two advantages of using differences rather than ratios.     

A note on the use ofregression methods in population estimates

Evidence which has emerged in the past few years indicates that the relative accuracy of population estimates derived from the ratio-correlation method and the difference-correlation method varies from state to state. In assessing the possible reasons why neither technique is uniformly more accurate, attention is focused on the temporal instability of the statistical relationships between symptomatic indicators and population change. The author concludes that further improvement in population estimates based on regression techniques is likely to be limited until demographers derive means of measuring and adjusting for these temporal changes.     

现行中国计划生育政策对中国人口安全的影响

本文从人口安全的定义出发,简单的分析了我国在发展中所面临的主要人口安全问题,并发现这些问题大部分都与我国的计划生育政策有着密切的关系。简要地阐述了我国现行计划生育政策的发展产生过程和主要内容。结合我国现行的“晚婚、晚育、少生、优生”的计划生育政策和我国主要的人口安全问题,从人口结构和人口素质两个方面,重点分析了我国计划生育政策对人口安全的影响。最后得出结论,要抓住现在的机遇期,调整现行的人口政策,最终实现中国人口与社会、经济、资源以及环境的协调可持续发展。     

Population estimates for Bangladesh: The use of a specific transitional population model

Summary The development of population in Bangladesh was affected by a succession of man-made and natural calamities, such as the Bengal Famine of 1943, refugee movements following the partition of India and Pakistan in 1947, devastating floods and cyclones around 1970, and the military action during the war of liberation. Though there had been a tradition of census taking and vital registration in Bangladesh, as part of the Indian sub-continent, extending for over a century, vital registration was so deficient as to be almost valueless, and there were gross misstatements of age and under-enumeration in the censuses. In the census of 1941, on the other hand, political manoeuvring led to a substantial overcount of the population. In this paper, Bangladesh population trends are studied within the broader framework of the subcontinent, taking account of plausible differentials. A considerable element of uncertainty was introduced into growth trends as a result of variations in the completeness of census-taking and of unrecorded refugee and labour movements across open land borders. In this connection the substantial inflationary bias associated with techniques of population estimation using the dual record system is discussed. The application of stable population models is even less justified in Bangladesh with its history of declining mortality. A transitional age structure model was constructed on the basis of the information available on declining mortality and accelerating growth and the model was made even more specific by modifications which took care of the impact of recent calamities and of unrecorded migration. The population base of the census of 1961 was adjusted in accordance with this model. The local mortality age pattern was used in projecting the population by sex and age groups to the date at which the census was originally due to be taken in 1971, and to the date when it was actually taken in March 1974. The post-1970 calamities and their effect on mortality were ignored. The aggregate estimate of population of 72.9 million in March 1974 is slightly in excess of the census count (by about two per cent) reported provisionally as 71.3 million. The excess in our estimate could be accounted for by the losses due to cyclone and military action.     

The effect of undercount on the accuracy of small-area population estimates: Implications for the use of administrative data for improving population enumeration

The effects of underenumeration on the accuracy of alternative methods of population estimation have not been sufficiently analyzed. Although the US Bureau of the Census has decided not to adjust either the counts or its estimates for underenumeration in 1990, the extent to which local population estimates may account for underenumeration is of importance both for those who may wish to adjust existing estimates and in anticipation of future census adjustments. This paper examines the accuracy of small-area population estimation methods with and without adjustment. Mean Percent Errors, Mean Absolute Percent Errors, and Mean Percent Absolute Differences between local estimates for 1990 and 1990 adjusted and unadjusted census counts are computed. Population estimates for 1990 made using housing unit, ratio correlation, and component methods are compared for 451 counties and 2,633 places in the states of California, Florida, Texas, and Wisconsin. An analysis of the data for counties shows little indication that local estimates more accurately estimate the adjusted than the unadjusted population counts. The results for places show clear improvements in accuracy for places in Florida and Texas. Implications of the findings for issues related to undercount adjustment and local population estimates are discussed.     

Criteria for selecting a suitable method for producing post-2000 county population estimates: A case study of population estimates in Illinois

We compared 2000 county population estimates for Illinois against 2000 census counts. Administrative records (ADREC) and ratio correlation (Ratio-CORR) methods were used to produce two sets of controlled county estimates for 2000; a third set represented an average of the estimates reached using these methods. Another set using the ADREC method was not controlled to any estimate. Also, the 2000 estimates were adjusted for undercount in the 1990 census. We compared performance of these methods with the performance of two naive models: (i) do nothing and (ii) constant growth rate. ADREC estimates were more accurate than estimates from the Ratio-CORR or Average method in terms of Mean Absolute Percent (MAPE) or weighted MAPE. Undercount adjustment in general improved the accuracy of the estimates for all three methods. A top-down or bottom-up approach worked equally well. As a single method, ADREC performed best.     

The impact of migration on the nonmetropolitan population age structure, 1960–1990

In this paper we examine the short-run impact of migration on the age composition of nonmetropolitan areas. Changes in age structure can have important consequences at the local level, and the influence of migration is particularly notable because it is highly age-graded, with different migration patterns found in various types of nonmetropolitan communities. Here we compare the impact of migration on age structures in metropolitan and nonmetropolitan areas across the last three decades. Within nonmetropolitan areas we also compare counties with colleges, commuting counties, agricultural counties and retirement counties. We conclude that several factors influence the impact of migration on age structure. Impacts will be greater in smaller than in larger population groups, and in areas that specialize in economic functions that impinge on a particular age group. But in general, migration adds young people to metropolitan areas and older people to nonmetropolitan areas. Differential impacts may be lessened in periods, such as 1970–80, when substantial population redistribution was underway. Nevertheless, prior and present fertility and mortality trends, and the cumulative history of migration well exceed the impact of migration on age in any ten-year interval.Abbreviations Metro Metropolitan - Nonmetro Nonmetropolitan An earlier version of this paper was presented at the annual meeting of the Western Regional Science Association, Wailea, Hawaii, 22 February 1993.     

The impact of taxation on the distribution of wealth in an economy with changing population

The paper investigates into the determinants of the personal distribution of income and wealth. In an overlapping generations model all individuals are assumed to be identical except for their inherited wealth. Since life time is random the bequest of an individual and thus the inherited stock of capital of its children are stochastic variables. Taxation and social security contributions affect life cycle savings, bequests, and, eventually, the distribution of income and wealth in the society. It is shown that, in general, higher tax rates reduce distributive inequality as long as the rate of interest is exogenously given. In steady state, however, where the rate of interest is determined endogenously, increasing taxation and higher social security payments both diminish the capital labor ratio so that the rate of interest rises. If this interest effect is strong enough then it may outbalance the tendency toward more equality because higher interest rates enhance initial differences in the distribution of both income and wealth and, eventually, the inequality in the distribution of income and wealth in the society.     

The changing impact of white migration on the population compositions of origin and destination metropolitan areas

Increased migration to the sunbelt and the metropolitan-nonmetropolitan "turnaround" represent departures from long-standing redistribution trends. Although these patterns have been examined from a number of perspectives, their consequences for individual metropolitan areas have not yet been brought to light. In the present study, stream-disaggregated data for the late 1950s and late 1960s are employed to assess the impact of recent migration on the sizes and compositions of white populations in thirty-one large metropolitan areas. Most large northern SMSAs have been experiencing the "new" migration patterns since the late 1950s. They have incurred net out-movements of whites to both metropolitan and nonmetropolitan areas. In their exchanges with nonmetropolitan areas, however, they have managed to retain greater numbers of college graduates and professional workers. Southern and western SMSAs did not sustain losses to nonmetropolitan areas during either period. They did appear to gain both total and high status population as a result of interregional metropolitan redistribution.     

United States population estimates and components of change: 1970 to 1987

This report analyzes year-to-year change in the US population from 1970 to 1987, including natural increase and net civilian immigration. Data are drawn from Current Population Reports. 1) The January 1, 1988 total population including Armed Forces overseas was over 245 million. This reflects a .9% increase over January 1, 1987, and an increase of 18 million since the April 1, 1980 census. 2) In the beginning of 1988, Whites numbered 206,979 million, Blacks 30,083, and Blacks and other races 38,130. 3) The crude birth rate dipped from 15.9 in 1980 to 15.6 in 1987; there is no evidence of a consistent trend since 1980. 4) The 3.8 million births in 1987 reflect a continuation of the gradual increase births that has been occurring since the mid-1970s, an increase attributed to Baby Boomers. 5) There was an 8.7/1000 death rate in 1987. This rate has fluctuated in the 8.5-8.7/1000 range since 1977 after declining from 9.4/1000 in 1972. The 2.1 million deaths in 1987 continue the gradual increase that has occurred since the end of the 1940s. This increase is attributed to the growth in population and to the population's continued aging. 6) Net immigrants/1000 population dropped slightly to 2.5 in 1987, down from 2.7 in 1986 and 3.7 in 1980. 7) Rates of growth for both Blacks and Whites have declined substantially since 1960; Blacks declined by about 1/3 (from 2.2%) and Whites by more than 1/2 (from 1.5%). The population of other races increased by 4.5% in 1987. The Black population grew by 1.5% in 1987, compared with a growth of .7% for the White population.     

Improvingaccuracy in multiple regression estimates of population using principles from causal modelling

This paper reports a mildly restricted procedure for using a theoretical causal ordering and principles from path analysis to provide a basis for modifying regression coefficients in order to improve the estimation accuracy of the ratio-correlation method of population estimation. The modification is intended to take into account temporal changes in the structure of variable relationships, a major element in determining the accuracy of post-censal estimates. The modification of coefficients is conservative in that it uses rank-ordering as a basis of change. Empirical results are reported for counties in Washington state that demonstrate the increased accuracy obtained using the proposed procedure.     

The impact of delayed maternity on foetal growth in Spain: An assessment by population attributable fraction

Background

Delayed childbearing is considered a risk factor for maternal–foetal health. As in other higher-income countries, in Spain age at maternity has steadily increased during the last two decades.