Johann Hari, our favourite non-economist and always game for a bit of silliness on economic history, tells us:
After slavery was abolished in 1833, Britain's GDP fell by 10 percent. (src, via)
I assume he means immediately after 1833, rather than at some point after 1833 (
e.g., 2009). If you check that then you find that while his specific claim is not only incorrect but almost certainly irrelevant, he does accidentally hit on nearly the correct figures. However, he appears to imply that slavery is good for GDP, which surely must make him almost unique in the Western world. Certainly any good Marxist would want to disagree with him, but so also should any good classical or neo-classical economist.
Before we look at the numbers, let me me explain why theory runs against that conclusion. The whole aim of any economy is that demand can be satisfied. But slaves are not very prolific consumers, so slavery restricts the market which can be served and is thus bad for the economy. Slavery is also a pretty inefficient way to obtain output. Ending slavery would free former slaves to consume more, which would in the long run more than compensate for the loss of output which might occur in the areas in which slaves were previously exploited.
Put another way, I suggest that Hari is committing the old fallacy of equating benefits to certain capitalists with benefits to the economy as a whole. 'What's good for Ford is good for America,' ran the old slogan, but it was never true. In a similar way, though the sugar plantation owners might have 'lost' by not being able to exploit the labour of their fellow-men, the domestic economy would gain by being able to sell to them instead. And what British consumers might 'lose' by not being able to buy cheap sugar should in the long-run be more than compensated by the ability of British industry to export textiles and other products to the former slaves.
Thus runs the theory, but what of the figures? The best figures I could obtain were constructed from records for British Guiana, from 1832–52, and were published in 1972 (
src) [1]. Let me set the historical scene briefly, because Johann Hari hasn't even looked at the right place. The Act abolishing slavery was passed in 1833, but the institution of slavery did not pass into history in that year. A six-year 'apprenticing system', shortened to five years through popular pressure, was implemented, so that the time when slavery was abolished was, in fact, 1838–39. And slavery was abolished in Great Britain a lot earlier than 1833: the 1833 Act abolished it in the rest of the empire. So Hari's study of Great Britain's GDP in 1833–34 is completely irrelevant, both geographically and chronologically.
Then let us look at the British Guianese economy from 1832 to 1838, while the apprenticeship system was going on. We find that it was basically stuck: GDP bounced around, going up a bit then down a bit. Sadly, no figures for the period of slavery proper were forthcoming. When slavery was finally done away with, GDP fell by about 10%, but across two years rather than one. Thereafter, the British Guianese economy motored away.
Drilling into the figures, you can see that the chief loser was, as expected, the sugar plantations, which lost a lot of cheap labour. The British Guianese economy's sole export was raw sugar, and they lost over a third of their exports in the two years around emancipation. The average growth in sugar exports from 1838 to 1842 was -9.72%. However, the domestic non-export economy
grew in the same period at an average annual rate of 7.72%. The British Guianese economy as a whole soon left behind the one-off shock of releasing its slaves, and entered growth instead of the stagnation it had apparently been suffering earlier [2].
In other words, slavery isn't good for economies. If British Guiana is typical of the British Empire at the time, slavery, or at least the interim apprenticeship system which retained many of its characteristics, slows economies down even as far as stagnation. Releasing slaves causes some economic dislocation — although nothing to compare with the dislocation caused by enslaving people in the first place — but once the slaves are freed, the economy grows more rapidly afterwards.
Curious, isn't it? Freedom works.
[1] This is only one paper, using constructed indices. In other words, this is all heavily-caveated. I am always happy to take other evidence on board, especially if it is a good review article which takes a broad view of the best available studies.
[2] The subsequent history makes very interesting reading. You can see all sorts of themes cropping up: on the positive side, voluntary co-operation and the ability of a liberated market to respond to needs; on the negative side, capture of the authorities by special interests and the pernicious effects of government sale and purchase to regulate wages and prices.