December 1, 2008
nnyq.com
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Define the "era of civilization" to be the last twelve millenia.
Proposition 0: the era of civilization has been an era of economic growth.
I think this will be accepted: World GDP in 10,000BC cannot have been as much
as ten times SubSaharan African GDP today, which is less than world GDP today.
Proposition 1: the era of civilization has been an era of accelerating economic
growth.
I have not heard this proposition expressed explicitly, but suspect it is true.
Towards the end of the era, world GDP has increased several percent per year
for several centuries. Surely growth was slower at the beginning and middle of
the era.
Question: Is proposition 1 correct, and if so, why has growth accelerated? An
answer with citations to sources would be appreciated.The key problem is evaluating your proposition is to find suitable data to test
it against. Fortunately, J. Bradford DeLong of the Department of Economics,
U.C. Berkeley has done some good homework for us to provide estimates of the
data we need to test you proposition. You will want to read his
paper, “Estimating World GDP, One Million B.C. – Present” which can be found at:
http://www.j-bradford-
delong.net/TCEH/1998_Draft/World_GDP/Estimating_World_GDP.html
Of particular interest are his estimates of World GDP from for the last 12
millennia. Three estimates which show similar trends are shown in a table and
graph near the end of his article. His plot is log-log, and the trends can be
described as piecewise linear with changes in slope approximately 9000, 3000,
150, and 60 years before present. A straight line on a log-log plot represents
a power relationship (in this case, GDP is proportional to time to some power),
where the power is the slope of the line on the log-log plot. For growth to be
accelerating, the power must be greater than one. Before 9000 BP, the power is
about .5; then it decreases to about 3, slowed to about 1.3, increased again to
about 2.5, and appears to have slowed to below 1 in the last 20 years or so.
Thus, if DeLong’s estimates are to be believed, growth was indeed slow in the
first 3000 years or so of your “era of civilization” but has been generally
accelerating with occasional blips since then. As to why the growth patterns
have been as they are, it appears that the driving factor has actually been the
patterns of growth in world population. The GDP per capita has also increased,
but generally more slowly than population. The leveling off in the last 20
years also appears to be a direct consequence of a slowing of population growth.
You may also wish to consult the book “The World Economy: a Millennial
Perspective” by Angus Maddison, which provides similar population and GDP data
for the last 2000 years. Information should be available at theworldeconomy.org
http://www.theworldeconomy.org/about.htm
although, when I checked, I was only able to viewed the Google cached pages of
the site.
A Google search on
World GDP
Is sufficient to turn up these and other useful references.I should have separated the answer to the second half of your question into a
separate paragraph, but I think the answer is there (unless I misunderstood
something): The World GDP trends (whether accelerating or not) are dominated by
population growth. While per-capita GDP has also changed substantially over
time, population growth has been so much faster that the per-capita changes
have only a minor influence on the World GDP trends. Graphs for population,
World GDP and per-capita GDP are all provided in the DeLong paper.
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