# Extrapolation Methods

## Abstract

Trend extrapolation methods are those in which future values of a variable are determined solely by its historical values. These methods have often been used for constructing population projections and can be organized into three categories. S*imple extrapolation methods* are those that have simple mathematical structures and require data for only two points in time. *Complex extrapolation methods* require data from a number of points in time, have more complicated mathematical structures, and require statistical estimation of the model’s parameters. *Ratio extrapolation methods* express the population of a smaller unit as a proportion of the population of a larger unit. In this chapter, we describe and illustrate a number of trend extrapolation methods and evaluate their strengths and weaknesses when used for state and local population projections.

## Keywords

Base Period Extrapolation Method Population Projection ARIMA Model Franklin County## References

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