Addenda to the previous blogpost “Economic growth in ancient Greece“. I argue that certain estimates made by Ian Morris under-compute the implied growth rates in the “per capita income” of the ancient Greeks. With a proper computation Morris’s estimates simply become unbelievable. This post does a kind of reductio ad absurdum using Morris’s own assumptions.
The Calculations of Ian Morris
In the previous post, I mentioned that Ian Morris simultaneously claims a manifold increase in the population density of Greece in the period 800-300 BCE and a 50-100% increase in Greek living standards. These combined claims imply an unbelievably large increase in the output per capita of ancient Greece.
Morris 2004 suggests consumption per capita rose 0.07-0.14% per annum in those 500 years. As far as I’m concerned these are basically fabricated out of thin air, but I’ve uploaded the 3-page extract of Morris’s own description from pp 724-6 so you can judge for yourself. For now I just assume those figures are real. Morris compares these growth rates of consumption per capita with data from England and the Netherlands a millennium and a half later. He concludes:
“The performance of the Greek economy in the first millennium BC was a whole order of magnitude lower than that of post-Industrial Revolution Britain, but it bears comparison with the some of the most dynamic pre-industrial economies that we know of.”
0.07-0.14% per annum may seem modest enough to be believable, but Morris grossly underestimates the total growth in output per capita required to generate that long-term improvement in living standards.
According to Morris 2005 [pg 7-8] the population density of ancient Greece went up from 3-4 people per km2 at the end (?) of the Greek Dark Ages circa 800 BCE to 12-15 per km2 by 500 BCE. Thus, population density jumped 3- to 5-fold.
In other words, although the land was supporting many many many more people, the ancient Greek economy was not hitting a Malthusian resource constraint. Land per capita was falling, but income per capita was not. To the contrary, according to Morris, living standards were rising. But he apparently does not realise that in order to keep income per capita just constant, even before factoring in the improvement in living standards, there must have been a substantial advance in productivity, whether in yield per hectare of land or in labour productivity.
The combined changes in population density and living standards imply:
- [low estimate] 3x population density + 1.5x living standards = 450% growth in output per capita, or 0.3% per annum over 500 years
- [high estimate] 5x pop density + 2x living standards = 1000% growth in output per capita, or 0.46% per annum over 500 years
But that’s still an undercomputation. Morris assumes consumption = 90% of income in 800 BCE and 75% of income in 300 BCE. When that’s factored in, then the growth rates in “GDP per capita” implied by Morris’s own assumptions would be 540% to 1200%, or 0.34% to 0.5% per annum over 500 years.
0.34-0.5% per year for 500 years. Is that really believable ???
Consider the growth rates in Britain’s GDP per capita, as estimated (with real data, despite imperfections) by Broadberry et al. (Table 5.07) :
According to the rival Clark data, the growth rates are even lower !
So what could have possibly caused such high sustained rates of growth in ancient Greek productivity ??? Remember, there is little evidence of consequential technological progress over this period.
I can believe in the modest rise in consumption living standards. But I cannot believe that population density even tripled, let alone quintupled.
A reader asked me why, in the previous post, I barely considered “Smithian” growth as a cause of the economic expansion in ancient Greece. That represents the gains from increasing the volume of trade and the specialisation of production, especially when previously isolated or autarkic regions are integrated into a single market. As Peter Temin argued in The Roman Market Economy, the gains from market integration could last a while even if they eventually face diminishing returns. I don’t discount that might have happened in the ancient Greek case. But I can’t believe that gains from integrating the Aegean, the lower Black Sea area, and possibly the Ionian sea region could have been as great or prolonged as the Roman creation of a “Mediterranean Free Trade Zone”, which contained much of the most densely populated and advanced parts of western Eurasia. Not to mention, there was much more economically relevant technological progress under the Roman empire than in classical Greece.