Abstract

The history of the official U. S. projections of population and house-holds in recent decades is briefly reviewed, with particular attention to methodology and the relation of the methodology to the accuracy of the projections. The introduction of the cohort-component procedure in the 1930’s opened the way for separate analysis of the trend of the components of births, deaths, and net immigration in connection with making population projections. As a further development, the period-fertility method of projecting births gave way in the 1960’s to the cohort-fertility method. Consideration is now being given to various methods involving parity-progression procedures. Some alternative methods and problems of measuring the accuracy of population projections are then considered. The percent “error” in the projected population growth, by components and age, and the range from high to low expressed as a percent should also be examined in addition to the percent “error” in the total population. However accuracy is measured, the projections made in the 1930’s and 1940’s were often wide of the mark, and those made in the 1950’s and 1960’s failed to anticipate the sharp changes which occurred, even though the actual figures usually fell within the range projected. Elaboration of projection methodology has not resulted in any great increase in the precision of the projections, largely because birth rates have fluctuated widely, and the fluctuations have proven difficult, if not impossible, to predict. The projections of households have had a roughly similar history, and the methods and problems of evaluation are somewhat similar. Their development has been characterized by the introduction of alternative and changing “headship” rates and increasing disaggregation of the data and procedures. The paper concludes with some generalizations based on U. S. experience. Although refinement of methods may contribute little to accuracy, accuracy is only one aspect of the usefulness of projections. The need for conditional projections and their analytical usefulness are such that there is no question that we should confidently continue to make them.

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References

Davis, Joseph S. 1949. The Population Upsurge in the United States. War-Peace Pamphlets No. 12, Food Research Institute, Stanford University.
Dorn, Harold F. (
1950
).
Pitfalls in population forecasts and projections
.
Journal of the American Statistical Association
,
45
(
251
),
311
334
. 10.2307/2280290
Grauman, John V. (
1965
).
Success and failure in population forecasts of the 1950’s: a general appraisal
.
Proceedings of the 1965 World Population Conference (Belgrade)
,
3
,
10
14
.
Hajnal, John (
1955
).
The prospects for population forecasts
.
Journal of the American Statistical Association
,
50
(
270
),
309
322
. 10.2307/2280963
Huyck, Earl, Akers, Donald S., and Johnston, Denis. 1963. Projections: an overview. Paper at the annual meeting of the Population Association of America in Philadelphia.
Muhsam, H. V. (
1956
).
The utilization of alternative population forecasts in planning
.
Bulletin of the Research Council of Israel
,
5
(
23
),
133
146
.
Muhsam, H. V. (
1965
).
The use of cost functions in making assumptions for population forecasts
.
Proceedings Of the 1965 World Population Conference (Belgrade)
,
3
,
23
26
.
Myers, Robert J. (
1954
).
Comparison of population projections with actual data
.
Proceedings of the 1954 World Population Conference (Rome)
,
3
,
101
111
.
Pearl, Raymond, & Reed, Lowell J. (
1920
).
On the rate of growth of the population of the United States since 1790 and its mathematical representation
.
Proceedings of the National Academy of Science
,
6
(
6
),
275
288
. 10.1073/pnas.6.6.275
Shryock, Henry S. (
1950
).
Forecasts of population in the United States
.
Population Studies
,
3
(
4
),
406
412
. 10.2307/2172503
Shryock, Henry S. (
1954
).
Accuracy of population projections for the United States
.
Estadistica
,
12
(
45
),
587
598
.
Sykes, Z. M. (
1969
).
Some stochastic versions of the matrix model for population dynamics
.
Journal of the American Statistical Association
,
64
(
325
),
111
130
. 10.2307/2283723
Taeuber, Irene B. (
1944
).
The development of population predictitons in Europe and the Americas
.
Estadística
,
2
,
323
346
.
Whelpton, P. K. (
1928
).
Population of the United States, 1925 to 1975
.
American Journal of Sociology
,
34
(
2
),
253
270
. 10.1086/214667