Note 66 — II. ITS FREQUENCY, AND THE CAUSES THEREOF.

“Had the rate of the annual increase of the numbers living under the age of five (3.13 per cent.) resulted entirely from the increase of births in a permanent population, the number of births of 1855 (in the districts where the ratio of the registered deaths to the population was greater than one to sixty-three, 166 of the 331 towns) would have been 24,457, instead of 23,481, the number registered. On the other hand, had the increase resulted wholly from migration, (the annual number of births in the permanent population being constant,) the number of births would have been only 22,956. The number of births registered is somewhat nearer the latter than the former of these two values.

“Assuming the correctness of the births, deaths, and population, in the selected districts, it appears that 35 per cent. of the increase of the population under the age of five was due to births in the permanent portion of the population, and 65 per cent. due to the movement of the migratory portion; also, that 38 per cent. of the increase of population at all ages was due to excess of births over deaths, leaving 62 per cent. to be accounted for by excess of immigration over emigration.”—Elliott, The Laws of Human Mortality in Massachusetts; Proceedings of Am. Assoc. for Adv. of Science, Montreal, 1857, p. 57.