| Number Whose Age Was Reported | Congenitally Deaf | Per Cent | |
| 1880 | 22,473 | 12,155 | 54.7 |
| 1890 | 37,204 | 16,866 | 45.8 |
| 1900 | 35,479 | 12,609 | 35.3 |
If we assume that the proportion of the congenitally deaf to all the deaf in each census was the same that it was among the cases in which the age of the occurrence of deafness was reported, we have this table to show the number of the congenitally deaf and the ratio of the deaf among the population.
THE CONGENITALLY DEAF ACCORDING TO NUMBERS ASSUMED
| Assumed Number of Congenitally Deaf | Ratio Per Million of Population | |
| 1880 | 18,531 | 369 |
| 1890 | 18,375 | 293 |
| 1900 | 13,286 | 175 |
These tables are taken from Annals, li., 1906, p. 487.
[60] In the three schools where an increase in congenital deafness appears to be found, namely, those of Michigan, Wisconsin and Ohio, a partial explanation probably lies in the fact that in these states a number of day schools have been created of late years, which are not likely to draw congenitally deaf pupils to the extent that the institutions do, thus leaving a larger proportion for the latter. See also E. A. Fay, op. cit., p. 125.