My research into over 100 defections of MPs and former MPs over the century from 1910 to 2010 shows that although most defectors go alone, they are linked by common characteristics and there are long term patterns to defections.
1 Defectors more often defect for better prospects (53%) than over policy differences (43%) and rarely over a personality clash (just 3% of defections).
2 Men are more likely to defect than women, after allowing for the greater number of male MPs.
3 Divorced MPs are more likely to defect.
4 MPs with a military background, especially those who achieved the highest ranks, were most likely to defect. Former teachers, farmers and ministers of religion were the least likely.
5 Those from a minority religion within their party were more likely to defect.
6 Richer MPs are more likely to defect that poorer ones. When they died, on average a defector left an estate worth £42,457, compared to the loyalists’ average of £28,919.
There was no significant regional variation around the country in defections, nor between urban and rural seats.
Defection is on average a career-enhancing move, with defectors more likely to achieve ministerial office and a peerage than loyalists.
Election years, both before and after the contest, are the peak times for defections.