1. In the year 1800, when the Parliaments of Great Britain and Ireland were fused by the Act of Union establishing the United Kingdom, the population of Ireland was of the order of 5 millions. By 1821 the figure had risen to 6·8 millions and in 1841 it was 8·2 millions. During the following decade the population fell by 1-6 millions to 6·6 millions. By the year 1861 it was only 5·8 millions and thereafter it continued to decline steadily, though not with such rapidity, until in 1911 a figure of 4·4 millions was reached. Owing to the disturbed state of the country in 1921, the next census was not taken until 1926, after the political change in 1922 when twenty-six of the thirty-two counties into which the country was divided were established as a separate political entity, the Irish Free State (later to become a Republic), while the remaining six were constituted as Northern Ireland and continued to form part of the United Kingdom. The population of the whole island in 1926 and again in 1951 was 4·3 millions, that is to say, it differed only slightly in 1951 from what it was forty years earlier in 1911—see Table 1. The population of Ireland has, therefore, remained virtually stationary at about 4¼ millions for almost half a century. The trend of Irish population since 1841 is in striking contrast with the trend in England and Wales for, whereas in 1841 the population of Ireland was more than one-half of that in England and Wales, today it is less than one-tenth; the Irish population has almost halved while that of England and Wales has almost trebled.
Characterisation of porcine circovirus type 2 in porcine circovirus disease cases in England and Wales