A study of the census of 1910 showing the distribution of the population of Porto Rico by race and by age periods gives some interesting information. If the situation given there is taken to be typical of general conditions, by considering the number of children of each class under one year of age, we find that the highest birth rate is among the mulattoes; next in order come the native whites of native parentage, next the blacks, and last the native whites of foreign or mixed parentage. The actual percentage of each class under one year of age is as follows: mulattoes, 3.9 per cent; native whites of native parentage, 3.6 per cent; blacks, 2.5 per cent; native whites of foreign or mixed parentage, 2 per cent. The percentage of the population under five years of age in each class tends to confirm this statement. It is as follows: mulattoes 17.9 per cent; native whites of native parentage, 14.7 per cent; blacks, 12.2 per cent; native whites of foreign or mixed parentage, 9.5 per cent.
While the mulattoes have the highest birth rate, it is also true that, as a general thing, they are the shortest lived of any of the classes mentioned. The class which generally has greatest longevity consists of the negroes; next in order come the native whites of mixed or foreign parentage, then the native whites of native parentage, and last, the mulattoes. Thus the order, as regards length of life, is nearly the reverse of what it is as regards birth rate.
It is observed also that while native whites of foreign or mixed parentage have a comparatively great length of life and a comparatively low birth rate, their children, who fall in the class of native whites of native parentage, have shorter lives and tend to produce larger families, than did the parents. In each class the females outnumber the males, the proportion being 100 females to 99.4 males for the total population, which, however, includes the foreign-born whites, where the males outnumber the females. In the classes of native-born citizens, the difference between the numbers of the sexes is greater than the ratio for the total population would indicate, being the greatest among the mulattoes, where the ratio is 93.6 males for every 100 females. In each class it is found that the women enjoy greater length of life than do the men.
The following table shows what proportion of the total number of each class of the population falls under the age groups designated.
| Table V | ||||||||||
| Negroes | Mulattoes | Native White of native parentage | Native White of foreign or mixed parentage | Foreign born white | ||||||
| Males | Females | Males | Females | Males | Females | Males | Females | Males | Females | |
| Under 5 years | 12.9 | 11.6 | 18.3 | 17.4 | 17.1 | 16.4 | 10.1 | 8.9 | .8 | 2.1 |
| 5 to 24 years | 42.3 | 42.5 | 48.2 | 47.1 | 46.2 | 46.4 | 45.6 | 45.9 | 18.8 | 20.8 |
| 25 to 54 years | 34.4 | 34.8 | 29.0 | 30.1 | 31.7 | 31.5 | 36.6 | 35.6 | 64.6 | 57.2 |
| 55 to 84 years | 9.7 | 10.5 | 4.4 | 5.3 | 5.0 | 5.0 | 7.4 | 9.3 | 15.6 | 19.2 |
| 85 years and over | .7 | .8 | .1 | .2 | .1 | .2 | .1 | .3 | .2 | .8 |
It will be noticed that above the age of 55 there is a larger proportion of women than men in each class. Judging the median age for each group to be the year which divides the total number of that group into two equal divisions, so far as number is concerned, we find the following median ages: blacks, 23; mulattoes, 18; native whites of native parentage, 20; native whites of foreign or mixed parentage, 22; foreign-born whites, 37. These results correspond exactly with the statements previously made regarding the longevity of each group. This would, of course, only give the median age for each class at the time the census was taken, in 1910, but as practically the same age distribution is also found in the census of 1899, it may be concluded that the results are approximately correct. This means that 50 per cent of each group does not live beyond the age indicated, and is sometimes known as the "mean length of life." Data for calculating the average length of life are not available.
A comparison of the age groups in the United States and in Porto Rico shows that the proportion in the younger ages is greater in Porto Rico than it is in the United States.
| Table VI | ||||
| Native white | Colored | |||
| Porto Rico | United States | Porto Rico | United States | |
| Under 5 years | 16.5 | 13.5 | 17.1 | 12.9 |
| 5 to 14 years | 26.3 | 23.0 | 27.1 | 24.4 |
| 15 to 24 years | 20.0 | 20.3 | 19.8 | 21.3 |
| 25 to 44 years | 25.4 | 26.5 | 24.2 | 26.8 |
| 45 to 64 years | 9.6 | 13.0 | 9.4 | 11.3 |
| 65 years and over | 2.2 | 3.6 | 2.4 | 3.0 |