LETTER:Voting patterns in Scotland

From Professor Iain McLean Sir: Donald Macintyre ("Half of British voters want Scottish parliament", 13 January) repeats a common error when he states "the current proportion of 72 MPs out of the UK total of 651 ... has remained roughly the same since the Act of Union of 1707". Both the numerator and the denominator changed during the 18th and 19th centuries.

In 1707, Scotland had 45 seats in a House of 558; in 1832, 53 out of 658; in 1868, 60 out of 658. The numerator settled at 72 in 1885 and has not varied by more than two since then. The denominator has ranged between 615 in 1922 and 707 in 1918. In recent decades it has crept up slowly and will be 659 at the general election.

As the ratio of Scottish to UK population has varied continuously, so, of course, has the level of representation of Scotland compared with the average for the UK. It is not the case, as Michael Quinlan ("That Scottish problem again", 2 January) and manyothers have said, that Scotland was given - still less guaranteed - over-representation at Westminster in 1707. Its seat share then was little more than half of its population share (see chart).

Scotland reached equality of representation between 1885 and 1918 and has been over-represented since 1922. Its population share has continuously declined, but there is no legal mechanism to change the ratio of seats between the components parts of the UK.

The increasing over-representation of Scotland is not due to the need for small seats in its scattered rural areas. That need has been constant and recognised since it was written into the rules of 1944.

Yours sincerely, IAIN McLEAN Official Fellow in Politics Nuffield College Oxford