army and navy serving in Ireland on the night of the 7th and 8th of April, but include the wives and families of such persons, and also soldiers on furlough:—
| Provinces | Population | |||
| 1851 | Decrease per cent. from 1841 to 1851 |
1861 | Decrease per cent. from 1851 to 1861 | |
| Leinster | 1,672,738 | 15.25 | 1,439,596 | 13.94 |
| Munster | 1,857,736 | 22.47 | 1,503,200 | 19.08 |
| Ulster | 2,011,880 | 15.69 | 1,910,408 | 5.04 |
| Connaught | 1,010,031 | 28.81 | 911,339 | 9.77 |
| Total of Ireland | 6,552,385 | 19.85 | 5,764,543 | 12.02 |
Civil registration, which began in England in 1837, and in Scotland in 1855, was not introduced into Ireland till the year 1864.
The subjoined table gives the number of births, deaths, and marriages, in each of the six years 1864-69, together with the estimated population of Ireland in the middle of the year:—
| Years | Estimated population |
Births | Deaths | Marriages |
| 1864 | 5,675,307 | 136,414 | 93,144 | 27,406 |
| 1865 | 5,641,086 | 145,227 | 93,738 | 30,802 |
| 1866 | 5,582,625 | 146,237 | 93,598 | 30,151 |
| 1867 | 5,557,196 | 144,318 | 93,911 | 29,796 |
| 1868 | 5,543,285 | 146,108 | 86,803 | 27,753 |
| 1869 | 5,546,343 | 145,912 | 90,039 | 27,364 |
Owing to the still defective state of registration in Ireland, the figures given above are returned as only an approximation to the real numbers.
The estimated population of Ireland, in the middle of the year 1870, was 5,525,210.
From the returns of the emigration commissioners, it appears that, of 2,249,355 emigrants who sailed from ports in the United Kingdom, between March 31, 1851, and April 8, 1861, no less than 1,230,986 were Irish; and from the returns obtained by the Registrar-General for Ireland, through the constabulary agents at Irish ports, during the like period, it is seen that as many as 1,174,179 persons were set down as permanent emigrants. The annual average emigration between 1831 and 1841 was 40,346, and from June 30, in the latter year, to the end of 1845, it averaged 61,242 per annum. In consequence of the potato blight, famine, and pestilence, the number rose to 105,955 in 1846; after which,
