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CHAPTER 10 - Coggle Diagram
CHAPTER 10
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characteristics at a present or near-future date, for which we have no immediately
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Nathan Keyftz (1968:27), one of
the world’s leading experts on population projection, put the matter succinctly. “The
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Estimates are necessary because it is practically impossible to collect data continuously, especially the amount and type gathered by government census operations.
In ordinary conversation, we tend to employ certain words that refer to anticipating
the future more or less interchangeably. Among the most frequently used are predict,
estimate, project, and forecast
Perhaps the most diffcult of these four is the frst, predict and the noun form,
prediction.
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Rather, it is an assessment of a future state of affairs, including the future state of
population characteristics, based on any or all of several sources: projection, scientifc theory, intuition, and even sheer guesses
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on demographic characteristics exists, such as Census years 1980, 1990, 2000, is
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Several methods of estimation are used by government census offces and academic
and private researchers.
An estimate is an attempt at arriving at the size of the current population based on data that refect current or recent conditions.
the linear model—also referred to as arithmetic growth—assumes
that the rate of change between two dates will be constant throughout the interval.
Four models, the linear, geometric, exponential, and logistic, are commonly
used, of which the frst and third were introduced in Chapter 8
a forecaster can take these nondemographic factors into account and, under the right circumstances, provide a useful depiction of
the shape of things to come
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geometric growth is more rapid than linear,
The assumption made by the geometric model, that increments (“interest payments”) are added to the population base (the “principal”) at the end of each year,
is not realistic
The logistic model assumes that neither absolute growth nor growth rates remain
constant over the period under observation.
the cohort survival method, assumes a
closed population in which net migration is set at zero.
Matrix-based methods were popularized by the leading U.S. demographer Nathan
Keyftz (1968, 1977).