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Marginality

Marg

The death of Gerald Kaufman (27th Feb 2017) raises the question of what is a marginal seat, as his, Manchester, Gorton must be one of the least marginal in the country. The BBC, in discussing the matter before the 2015 general election, stated,

"There is no fixed definition of a marginal: but if we choose to define them for the 2015 election as seats with majorities of 10% or less that require a swing of 5% for the incumbent party to lose, then there are currently 194 such marginal seats in Britain, of which 82 are Conservative, 79 Labour, 27 Lib Dem, three SNP, two Plaid and one Green." [BBC]

In the case of Manchester, Gorton, Kaufman took 67% of the vote with the 2nd and 3rd candidates tied on just under 10%. Clearly the percentage is more significant than the absolute majority as there is such wide variation between seats in the number of voters and, to a lesser extent the turnout.
The proposed boundary changes are (or would have been) another factor.

In practical terms for the MPs page, it is a question of what data is easily accessible and what will actually fit on the table. My initial thoughts are to show the percentage majority (e.g. 57% above) and some indication of the impact of the boundary changes.

Sources
parliament.uk BBC