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J. Bradford DeLong
Department of Economics, U.C. Berkeley
http://www.j-bradford-delong.net/
I take my estimates of human population from Kremer (1993), but it would not matter if I had chosen some other authority. All long-run estimates of human population that I have found are quite close together (with the exception of estimates of population around 5000 BC, where Blaxter (1986) (cited in Cohen (1995)) estimates a population some eight times that of other authorities). Note that this does not mean that the estimates are correct--just that they are the same.
Kremer (1993) sees human populations as growing at an increasing proportional rate from perhaps 125,000 in one million B.C. to 6 billion today. Population reached approximately 4 million by 10000 BC, 50 million by 1000 BC, and 170 million by the year 1. Population then reached 265 million by the year 1000, 425 million by 1500, and 720 million by 1750 before exploding to 1.2 billion by 1850, 1.8 billion by 1900, 2.5 billion by 1950, and 6 billion today. Up until 1950 Kremer calculates that the rate of growth of human populations was roughly proportional to their total level.
Angus Maddison (1995) has constructed estimates of real GDP per capita for the world from 1820 to 1992. His estimates are best thought of as Laspeyres purchasing power parity estimates in 1990 international dollars. That is, they:
All of these save the last is reasonabl--is in fact a way of proceeding vastly preferable to the alternatives. I will return to the last of these later. But first I want to extend Maddison's estimates backward before 1820.
If you plot the rates of world population growth against Maddison's estimates of world GDP per capita, you find a very high and significant correlation between the two from the early nineteenth century until roughly World War II. After World War II the demographic transition has begun to take hold in large parts of the world, but before World War II the higher is world GDP per capita, the faster is population growth--with a 1 percentage point per year increase in population growth associated with an increase in average world GDP per capita of $1,165 (with a t-statistic of 7.4 and an adjusted-R2 of 0.84).
If you are enough of a Malthusian to believe that this tight relationship before World War II is not coincidence but instead reflects a near-linear dependence of the rate of human population growth on the margin between actual production and bio-cultural subsistence, then you can use the fitted relationship between population growth and Maddison-concept GDP per capita to backcast estimates of world GDP per capita before 1820.
An alternative (preferred by Maddison) is to assume that GDP per capita was constant in Asia and Africa from 1500-1820, grew at 0.1 percent per year from 1500-1820 in Latin America and Eastern Europe, and grew at 0.2 percent per year from 1500-1820 in Western Europe (an estimate that Maddison attributes to Simon Kuznets (1973)); this alternative could then be backcast further by assuming that pre-1500 GDP per capita was constant at near-Malthusian bio-cultural subsistence.
I prefer the first alternative (and have used it). But I also report estimates using the second.
A large proportion of our high standard of living today derives not just from our ability to more cheaply and productively manufacture the commodities of 1800, but from our ability to manufacture whole new types of commodities, some of which do a better job of meeting needs that we knew we had back in 1800, and some of which meet needs that were unimagined back in 1800.
How much has this change--the fact that we make not just the same goods, but new goods and new types of goods--enhanced our material prosperity? Nordhaus (1997) provides perhaps the most eloquent and sophisticated argument that standard measures--like those of Maddison--that do not take explicit account of these factors grossly understate the rate of economic growth over the past two centuries.
I know that I at least would be extremely unhappy if I were handed my current income, told that I could spend it on goods at current prices, but that I was prohibited from buying anything that was not made before 1800. Yet Maddison's procedures would implicitly take such a reduction in the range of goods I could purchase as having no effect on my real income or real material standard of living.
But by how much has our power to make new things--not just the same things more efficiently--amplified our material prosperity?
In at least some models of growth in which the set of goods that can be produced expands, the correct measure of real output is proportional to the product of purchasing power (income divided by the average price of a good) and the number of goods that can be produced. As best as I can determine, about three-quarters of world expenditure today is spent on commodities that simply did not exist back in 1800. So I (somewhat arbitrarily) use this to assign an additional fourfold multiplication to output per capita since 1800 in addition to the increases in output per capita calculated by Maddison.
But since this--large--extra adjustment is not to everyone's taste, I also report the "ex-Nordhaus" series without the "new kinds of goods" adjustment.
The outcome of this set of calculations is thus seven series: Kremer's (1993) estimates of population; three estimates of GDP per capita (my preferred estimate, the constant-before-1500 estimate, and the ex-Nordhaus estimate); and three estimates of total world real GDP (capita (my preferred estimate, the constant-before-1500 estimate, and the ex-Nordhaus estimate).
They are reported in the table below:
Average World GDP per Capita
(1990 International Dollars)
Year |
Preferred |
Ex-Nordhaus |
Constant Pre-1500 GDP per Capita |
-1000000 |
92 |
340 |
115 |
-300000 |
92 |
341 |
115 |
-25000 |
92 |
343 |
115 |
-10000 |
93 |
344 |
115 |
-8000 |
96 |
357 |
115 |
-5000 |
103 |
381 |
115 |
-4000 |
109 |
406 |
115 |
-3000 |
113 |
420 |
115 |
-2000 |
112 |
415 |
115 |
-1600 |
121 |
449 |
115 |
-1000 |
127 |
471 |
115 |
-800 |
143 |
530 |
115 |
-500 |
137 |
509 |
115 |
-400 |
130 |
483 |
115 |
-200 |
113 |
420 |
115 |
1 |
109 |
404 |
115 |
14 |
102 |
380 |
115 |
200 |
98 |
362 |
115 |
350 |
94 |
350 |
115 |
400 |
97 |
360 |
115 |
500 |
102 |
379 |
115 |
600 |
104 |
387 |
115 |
700 |
112 |
414 |
115 |
800 |
116 |
430 |
115 |
900 |
131 |
486 |
115 |
1000 |
133 |
494 |
115 |
1100 |
124 |
459 |
115 |
1200 |
104 |
386 |
115 |
1250 |
99 |
367 |
115 |
1300 |
89 |
331 |
115 |
1340 |
109 |
406 |
115 |
1400 |
128 |
476 |
115 |
1500 |
138 |
512 |
115 |
1600 |
141 |
524 |
140 |
1650 |
150 |
556 |
155 |
1700 |
164 |
607 |
172 |
1750 |
178 |
662 |
190 |
1800 |
195 |
722 |
210 |
1850 |
300 |
788 |
300 |
1875 |
429 |
948 |
429 |
1900 |
679 |
1263 |
679 |
1920 |
956 |
1550 |
956 |
1925 |
1108 |
1735 |
1108 |
1930 |
1134 |
1716 |
1134 |
1940 |
1356 |
1915 |
1356 |
1950 |
1622 |
2138 |
1622 |
1955 |
1968 |
2505 |
1968 |
1960 |
2270 |
2792 |
2270 |
1965 |
2736 |
3251 |
2736 |
1970 |
3282 |
3768 |
3282 |
1975 |
3714 |
4119 |
3714 |
1980 |
4231 |
4533 |
4231 |
1985 |
4634 |
4797 |
4634 |
1990 |
5204 |
5204 |
5204 |
1995 |
5840 |
5641 |
5840 |
2000 |
6539 |
6103 |
6539 |
Total World Real GDP
(Billions of 1990 International Dollars)
Year |
Preferred |
Ex-Nordhaus |
Constant Pre-1500 GDP per Capita |
-1000000 |
0.01 |
0.04 |
0.01 |
-300000 |
0.09 |
0.34 |
0.11 |
-25000 |
0.31 |
1.15 |
0.38 |
-10000 |
0.37 |
1.38 |
0.46 |
-8000 |
0.43 |
1.61 |
0.52 |
-5000 |
0.51 |
1.91 |
0.57 |
-4000 |
0.77 |
2.84 |
0.80 |
-3000 |
1.59 |
5.89 |
1.60 |
-2000 |
3.02 |
11.20 |
3.09 |
-1600 |
4.36 |
16.16 |
4.12 |
-1000 |
6.35 |
23.55 |
5.73 |
-800 |
9.72 |
36.05 |
7.79 |
-500 |
13.72 |
50.90 |
11.46 |
-400 |
16.02 |
59.44 |
14.09 |
-200 |
17.00 |
63.05 |
17.19 |
1 |
18.50 |
68.65 |
19.48 |
14 |
17.50 |
64.91 |
19.59 |
200 |
18.54 |
68.80 |
21.77 |
350 |
17.93 |
66.53 |
21.77 |
400 |
18.44 |
68.40 |
21.77 |
500 |
19.92 |
73.90 |
22.34 |
600 |
20.86 |
77.39 |
22.92 |
700 |
23.44 |
86.97 |
24.06 |
800 |
25.53 |
94.70 |
25.21 |
900 |
31.68 |
117.52 |
27.73 |
1000 |
35.31 |
131.00 |
30.36 |
1100 |
39.60 |
146.91 |
36.67 |
1200 |
37.44 |
138.90 |
41.25 |
1250 |
35.58 |
132.01 |
41.25 |
1300 |
32.09 |
119.06 |
41.25 |
1340 |
40.50 |
150.27 |
42.39 |
1400 |
44.92 |
166.64 |
40.10 |
1500 |
58.67 |
217.64 |
48.70 |
1600 |
77.01 |
285.70 |
76.41 |
1650 |
81.74 |
303.24 |
84.53 |
1700 |
99.80 |
370.26 |
104.67 |
1750 |
128.51 |
476.75 |
136.67 |
1800 |
175.24 |
650.11 |
189.00 |
1850 |
359.90 |
945.60 |
359.90 |
1875 |
568.08 |
1256.10 |
568.08 |
1900 |
1102.96 |
2052.38 |
1102.96 |
1920 |
1733.67 |
2810.15 |
1733.67 |
1925 |
2102.88 |
3293.03 |
2102.88 |
1930 |
2253.81 |
3409.69 |
2253.81 |
1940 |
3001.36 |
4237.90 |
3001.36 |
1950 |
4081.81 |
5379.21 |
4081.81 |
1955 |
5430.44 |
6913.80 |
5430.44 |
1960 |
6855.25 |
8431.84 |
6855.25 |
1965 |
9126.98 |
10845.34 |
9126.98 |
1970 |
12137.94 |
13934.06 |
12137.94 |
1975 |
15149.42 |
16801.40 |
15149.42 |
1980 |
18818.46 |
20162.78 |
18818.46 |
1985 |
22481.11 |
23270.25 |
22481.11 |
1990 |
27539.57 |
27539.57 |
27539.57 |
1995 |
33644.33 |
32503.40 |
33644.33 |
2000 |
41016.69 |
38281.97 |
41016.69 |
Total World Population
(Millions)
Year Human Population (Kremer Series; millions)
-1000000 0.125
-300000 1
-25000 3.34
-10000 4
-8000 4.5
-5000 5
-4000 7
-3000 14
-2000 27
-1600 36
-1000 50
-800 68
-500 100
-400 123
-200 150
1 170
14 171
200 190
350 190
400 190
500 195
600 200
700 210
800 220
900 242
1000 265
1100 320
1200 360
1250 360
1300 360
1340 370
1400 350
1500 425
1600 545
1650 545
1700 610
1750 720
1800 900
1850 1200
1875 1325
1900 1625
1920 1813
1925 1898
1930 1987
1940 2213
1950 2516
1955 2760
1960 3020
1965 3336
1970 3698
1975 4079
1980 4448
1985 4851
1990 5292
1995 5761
2000 6272
Michael Kremer (1993), "Population Growth and Technical Change, One Million B.C. to 1990,"Quarterly Journal of Economics 108:3 (August), pp. 681-716.
Joel Cohen (1996), How Many People Can the Earth Support? (New York: W.W. Norton: 0393314952).
Angus Maddison (1995), Monitoring the World Economy, 1820-1992 (Paris: OECD: xxxx).
William Nordhaus (1997), "Do Real Wage and Output Series Capture Reality? The History of Lighting Suggests Not," in Timothy Bresnahan and Robert Gordon, eds., The Economics of New Goods (Chicago: University of Chicago Press: 0226074153).
Professor of Economics J. Bradford DeLong,
601 Evans Hall, #3880
University of California at Berkeley
Berkeley, CA
94720-3880
(510) 643-4027 phone (510) 642-6615 fax
delong@econ.berkeley.edu
http://www.j-bradford-delong.net/
This document: http://www.j-bradford-delong.net/TCEH/1998_Draft/World_GDP/Estimating_World_GDP.html