Economists have reported results based on populations for every country in the world for the past two thousand years. The source, McEvedy and Jones’ Atlas of World Population History, includes many estimates that are little more than guesses and that do not reflect research since 1978.

McEvedy and Jones often infer population sizes from their view of a particular economy, making their estimates poor proxies for economic growth. Their rounding means their measurement error is not “classical.” Some economists augment that error by disaggregating regions in unfounded ways.

…we haven’t just pulled the figures out of the sky. Well, not often.

McEvedy and Jones (1978_46ya, p. 11)

…In the past 20 years, economists have estimated empirical exercises that rely in part on a published work that reports the population of every country in the world starting in the year 1 AD or even earlier. The existence of such data surprises those familiar with research on population history; we have only a rough idea of the population of most parts of the globe before 1500. For many countries, the statistical lacuna extends closer to the present. Until the advent of modern censuses, which in most countries started during the 19^th century, reckonings of the total population for even the best-studied cases remain subject to considerable error.

These exercises typically rely on McEvedy and Jones’s Atlas of World Population History (hereafter MJ). Published in 1978, this work reports a population total for the countries of the world at intervals of a century or half-century. MJ did not disguise the rough nature of their data, as the epigraph notes, and we should distinguish what they report from the way others used their work. Several economists point to a US Census Bureau summary that appears to endorse MJ’s estimates. The Bureau simply notes that MJ’s estimates for world population are not too different from the other, earlier results.¹ As MJ state (ppg353–354), however, that agreement is largely by construction.

The drawbacks of using such data are numerous. MJ’s estimates, as they suggested themselves at the time of writing, lacked, in many cases, any firm foundation. Often, the estimates appear to reflect a judgment about the nature of the economy in question, rendering their use as economic proxies partially tautological. The MJ estimates are out-of-date for some countries; researchers have provided better figures in the past 40 years. Economists tend to dismiss measurement error issues by appealing to the implications of “classical” measurement error. MJ’s clearly stated rounding rules mean the measurement error is not classical. Non-classical measurement error create several opportunities for bias in regression models. Economists have compounded these weaknesses with unwise disaggregation practices.

Many economics articles, including several highly cited contributions in the leading journals, rely on MJ for econometric exercises. This research has appeared in the leading general-interest economics journals, in development and growth-oriented journals, and in the main field journals for economic history. Several of these papers have been cited many times.² The present paper raises serious questions about the results of any econometric exercise that relies on MJ.

… A hint comes from the suspiciously round progression of population figures for single countries.⁹ Table 1 shows the overall patterns; in many cases, MJ apparently devised a population estimate after deciding on a round figure for percentage growth. The many commonalities across countries are implausible. Individual country histories drive home the problem. In MJ’s reckoning, England’s population grew by 750,000 1600^–₅₀1650_374ya, and by another 750,000 in the next half-century (McEvedy & Jones1978, pg43). Austria added 250,000 people every 50 years 1650^–₁₅₀1800_224ya (ppg88–92). Thailand added 250,000 people in both the 16^th and 17^th centuries (pg193). Burma’s population growth during the same period was 500,000 per century.

Second, MJ apparently wanted their estimates to reflect their view that until the late medieval period, population grew at a constant rate. In disagreeing with an earlier author on the right total world population for the year 1000, MJ note that “our figure for AD 1, being 100m below the agreed figure for AD 1000, fits better on the sort of exponentially rising curve that everyone agrees best describes mankind’s population growth” (pg354). As the quotation implies, MJ also worried about consistency between theirs and earlier estimates. Caldwell & Schindlmayr2002 (pg199) call this “an example of a dangerous circularity”, while Biraben dismisses the MJ data after noting this fact.¹⁰