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RICE UNIVERSITY STUDIES
obtained were it possible to obtain GNP figures for individual
years prior to World War I or if the study were based on real
rather than on current data.
Our main interest in this data, however, is in showing the need
for careful analysis of long-term growth as well as growth in
the short term. Without sufficient long-term statistics, a Type-III
fluctuation may be misinterpreted as one of Type-II, and an
underestimate of the trend growth rate may be made. Indeed, this
has often happened in the past 30 years ; libraries and other institu-
tions have rapidly outgrown facilities constructed under the mis-
apprehension of future lower trend growth rates due to an analysis
of insufficient portions of their growth records.
Figure 19 exhibits the history of United States invention patents
issued from 1790 through 1966 (cf. Table III). This complex
graph contains fluctuations of all three types. There is an important
Type-III fluctuation during the Great Depression which increases
in its effect during World War II, and there are two others, from
about 1812 to 1822, and 1830 to 1845, There is a basic change in
the trend growth rate, a Type-II deviation, at about 1870 which
appears to correspond to the Type-II transitioħ observed in the
U.S. population curve (Figure 9) about 1880. And there are the
inevitable Type-I random fluctuations throughout the graph.
5. Conclusions
It appears to us that future research of a more complete and
detailed nature will bear out the following conclusions:
1. Exponential growth of library holdings will persist for the
foreseeable future. To maintain current growth rates, automa-
tion of the production of portions of the intellectual content, as
well as the production of books and equivalent forms of stored
information, will increase.
2. Growth curves of importance to library management consist
in general of piecewise exponential segments connected by transi-
tional fluctuations. Determination of the nature of the current
and short-term future portions of the curves is necessary for
realistic and practical planning purposes. Piecewise exponential
approximations are the simplest techniques for exhibiting the
structure of these growth curves.
3. As far as growth rates are important for planning purposes,
fluctuations of Type-III must be detected and ignored in the
evaluation of future requirements of a library.