¹ Since much of our data is based on information obtained in censuses, our terminal year is most frequently 1920 or 1921 rather than 1914. Much of the international movement of population of the decade 1910–1920, in which we are interested, had taken place by 1914.

² The adoption of this procedure does not mean that we believe that population movements are exogenous in a causal sense. But it is not the purpose of our paper to explain population movements.

³ It can be argued, on Heckscher-Ohlin grounds, that if people and capital move internationally, the growth of commodity trade would tend to be checked. The argument does not apply, however, as long as some countries remain very highly specialized (e.g., very resource-abundant countries). Further, the decline of transportation costs lowers barriers to trade.

⁴ The figures available for Italy are particularly hard to interpret. Alternative figures give much higher estimates of emigration from Italy than we have used in the period 1900–1910. Our conclusions, however, are not affected in any crucial manner by the use of other estimates.

⁵ The very large numbers of Irish among emigrants from the United Kingdom, are seldom noticed and insufficiently appreciated. Some indication of distortion arising from neglect of this point is given by Butlin, Noel in his article, “A Plea for the Separation of Ireland,” Journal of Economic History, 28 (June 1968), 274–291.Google Scholar

⁶ It is interesting that the United Kingdom and the United States had roughly similar proportions of the population in the 0–14 year and in the 15–64 year age groups, from 1880 to 1910. U.S. rates of natural increase were higher than those for the U.K. In the U.K., emigration. of those in the 20–40 year age group lowered the proportion in the 15–64. year age group and thus raised the ratio in the other age groups, including that of the 0–14 age group. In the U.S., immigration of disproportionately, high numbers in the 15–64 age group lowered the proportion in the 0–14 age group. These two movements brought the proportions of each country into conformity with those of the other country.

⁷ Residents of the United States did import substantial amounts of capital, especially for financing railway building, in this period. At the same time, however, they exported considerable amounts of capital. The result was that on balance, there was a net capital inflow of consequence only in some years of the 1870's and 1880's.

⁸ It is interesting, however, that even the United States appeared to have a short run problem of this kind in the late eighties and early nineties. The great expenditures of the eighties on railways and settlement of the plains did not provide their payoff until the mid to late nineties, a phenomenon which is reflected in the apparently relatively low productivity growth of the eighties.