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I'm wondering if historians have figured out a way to combine historical datasets perhaps by using some kind of economic equivalent of Dendrochronology, where lots of different historical datasets are overlayed (using their similarities) to create a continuum of information that extends far back into the past.

If such an effort was made, it might be possible to do some interesting things like estimate the cost of the Great Pyramid of Giza as a percentage of Egypt's total Gross Domestic Product (GDP) at the time, and compare that to, for example, the amount that the US spent as a proportion of its GDP to land the first people on the moon.

For context, I'm studying infrastructure, what causes it to spring into existence, and how that has changed over the course of history. I'd really like to be able to figure out how the investment in infrastructure as a percentage of a society's GDP has changed over time. But I figure that it would be better to start with the more general tracking-economic-power question as a prerequisite.

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    Documenting preliminary research will improve both the probability of an answer and the quality of the answer(s). Still needs more research. Suggest you start with Wikipedia and then GDP.
    – MCW
    Commented Jul 2 at 8:58
  • I'm also somewhat skeptical about comparing GDP across fiat based and specie based economies. GDP is a monetary based measure, which would be of limited value in a pre-monetary economy. There are economic historians who write books on this topic, and I suspect that is one of the reasons that "book length answers" are out of scope on H:SE (? all SE?). This answer requires a book, and books have been written.
    – MCW
    Commented Jul 3 at 14:32
  • This is done by economists and economic historians so you might want to ask on Economics.SE instead. Historians are generally not sufficiently well trained in quantitative methods and economic reasoning to understand how this can be done (and is done). Rough estimates are imprecise and difficult but not impossible to make.
    – user103496
    Commented Jul 7 at 1:33

3 Answers 3

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TL;DR: Don't trust historical GDP data about pre-modern times

What are the problems with computing economic growth for earlier historical periods?

You have 6 problems with computing historical economic growth compared to historical climate:

  1. You need to answer the question: Growth of what? Income? Welfare? Wealth? Capital? The tax base? Since this is commonly done today and since you already mentioned the GDP, you seem to have income in mind. The GDP is a measure of income.

  2. The problem with measures like the GDP is that they are modern measures. Specifically, the GDP was proposed and outlined by the NBER report to congress led by Simon Kuznets in 1934. All GDP data older than that are approximated from other historical data and not usually considered reliable.

  3. The GDP does not measure every part of economic activity. For instance, it only measures commercial activity (i.e., not subsistence farming, private care work, the shadow economy (i.e., illegal activities)). The drawbacks are laid out in detail in the report linked above.

  4. The GDP depends on the price level. If your estimate for the price level is wrong, your GDP measure is wrong. The price level, in turn, is a composite index of the prices of commonly consumed goods (the 'good basket'), all of which have different price changes; what these goods are changes over time and varies between places. In modern economic statistics, you distinguish between nominal GDP (literally the amount of USD, GBP, EUR, JPY, CNY etc that was earned), inflation-corrected GDP (where you correct all the values for the inflation of the respective country) and GDP in chained prices (which also takes changes in the good basked into account). It is exceedingly difficult to do this for pre-modern times. You will also find that the price levels of different countries diverge quickly and that the GDP computed with those may not be consistent any more.

  5. Problem 3 (incomplete measurement of economic activity in data) is worse the deeper you go into history. This is because subsistence production was more common. Even if you disregard that, it is questionable if the income concepts for modern and pre-modern states and for different pre-modern regions are consistent.

  6. Before the emergence of modern statistical offices (at most about 200-300 years ago), the data you have gets much worse. If you are lucky, you have data on taxation. Taxation is what countries cared about before they cared about economic growth. But since the focus is different, this may not be reliable indicators for income. Also, there were many different ways to define the tax base (income? wealth? the size of your house? the number of windows in your house? ...). Furthermore, surviving tax records are also not too abundant.

So what do we have?

That said, there are historians, primarily Angus Maddison (his book ''Countours of the world economy AD 1 - 2030'', Oxford University Press 2007, is one example, but he has more writings), who are trying to do this. For some countries, you will find official estimates for economic data, that go a long way back (almost 1000 years for the UK, see here), but this is the exception. Also, you should exercise a lot of caution when working with such data. Almost everything in there is approximated in modern times and uses a ton of assumptions that may or may not be true. There are also attempts to assess economic development based on archaeological data. But I don't thing we're far enough along with this that you could expect a full record (instead of the odd data point every few hundred years, which may or may not be comparable to other data points).

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    Nice answer. But for #3, GDP includes (an estimation of) shadow economy. I would not be surprised if there were also an estimation of subsistance farming or private care, either.
    – SJuan76
    Commented Jul 3 at 17:33
  • @SJuan76 Thanks, you are right; it is supposed to be part of the GDP by definition (as it's part of what is produced) and there are efforts under way to estimate and include these activities. (The UK ONS for instance lists a few non-market categories in it's national accounts.) This does not make it any less difficult and error-prone to estimate it, especially for earlier historical times. The report (link in #2. above) discusses these limitations in Chapter 1, Section 3.
    – 0range
    Commented Jul 3 at 20:44
  • Very clear. Maybe slightly off topic, but not too much. Could I recommend the excellent book "Why the West rules. - for now" by Ian Morris for another look at development over the ages.
    – cucu8
    Commented Jul 11 at 10:39
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Prior to mechanization and exploiting alternative energy sources (like fossil fuels, wind and water), the economic unit we really care about was the calorie.

Societies lived and died on how many calories of food it produced for people, which determined the workforce size. How much work did it require to generate those calories? How much surplus work was available to be harnessed?

And animals became just another way to turn food calories into work.

We can see this happening in the relatively recent era. Malthusianism describes how a society gets richer, generates more food, has a population increase, and the wealth per person falls back to near-starvation levels. Then a disease or famine hits, the population falls, and food production doesn't fall as far, resulting in a society richer per person, and population growth occurs as fewer children die in infancy.

Graphs of (estimated) GDP per capita vs (estimated) population levels produce this relatively neat feedback loop, as increased wealth per person leads to increased population which drops wealth which causes population to fall, which increases wealth per person, etc.

Modern industrial societies have escaped this trap, with a quite small percentage of labour and societies' available energy being spent on feeding humans. Without being "trapped" with most of our energy being put towards food, we use work to solve other problems - build mines, infrastructure, devices, etc - that in turn yield more work output. This causes a divergence in the GDP per capita - the economic activity we can do per person - that the pre-industrial world never experienced anything of similar magnitude.

And we have relatively good data going back to the edge of this industrialization, where the vast majority of the "work" a society does is dedicated to producing food to feed the people. And you can't get much poorer than this, because if you do your population starves, and to the best of our ability to tell nobody got much richer (per capita) than this.

This, in turn, means we can look at the infrastructure projects and work out how many food calories it would take to build them - how many worker-hours as well as animal-hours - and look at the total capacity of the society (in terms of calories of food grown) and compare those two numbers.

This information is often available even if more detailed economic data is missing. Taxes are often levied on food produced, for example, so we have extensive records of food production levels. For the Egyptians, we even have records of employment - from salary negotiations, labour disputes, etc - going back 1000s of years, plus information about how the various structures were built (we know how the Egyptians built pyramids because they wrote it down and we can read it - ignore the "ancient mysteries" nonsense).

There are a few limits to our knowledge. Like, how hard was it to produce those levels of food? But even there we can find census information, and make assumptions.

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Gross domestic product or GDP is probably not the best way to go about it, particularly when comparing ancient economies. Today, in a global world, gross national product, encompassing GDP + foreign economic activities and financial investments seems a more appropriate metric. On the other hand, energy intensity, i.e. calories per unit product may only be referenced to GDP, for bridging with ancient economies, but it would not be a fair comparison because of globalization of economic returns.

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