Dr Renwick:

Some people have expressed a concern that, because the boundaries are old, they have had a marked biasing effect on election results. The evidence shows that, in fact, the effect is quite small. There are a number of factors that can mean that a vote cast for one party has more weight in the overall results than a vote cast for another party. The main factors that shape that are turnout. Turnout in Labour seats tends to be lower than turnout in Conservative seats, and therefore Labour MPs tend to be elected with fewer votes than Conservative MPs.

The second big factor is the efficiency of the distribution of votes across the country. Between 1997 and 2005, the Labour vote was much more efficiently distributed than the Conservative vote. Labour had tended to win more marginal seats and did not waste, as it were, lots of votes in constituencies that it lost, whereas in the last several elections the Conservatives have had the more efficient distribution of votes across the country. Those are the main factors that lead to biases in terms of the overall election result.

There is also some effect from the distribution of constituencies—both the distribution between the countries within the United Kingdom and the distribution within those countries. At recent elections those effects have produced small biases in favour of Labour, but those are fairly small biases. I am sure you will hear much more on this when you hear evidence from Charles Pattie and David Rossiter, who are the real experts on this, but the consensus in the literature on this is that that effect is fairly small. The effect that really matters is the effect on the democratic principles, not the outcome of elections.