Start with a few facts:
2007 Constituency results for Scottish Labour – 648,374, 32.2%
2011 Constituency results for Scottish Labour – 630,461, 31.7%
So down 18,000 votes and 0.5%.
2007 Regional List results for Scottish Labour – 595,415, 29.2%
2011 Regional List results for Scottish Labour – 523,559, 26.3%
So down 72,000 and 2.9%
2007 Constituency List differential – (53,000)
2011 Constituency List differential – (107,000)
As a comparison for the SNP:
2007 Constituency List differential – (31,000)
2011 Constituency List differential – (26,000)
Whilst the stagnation of the constituency Labour vote (cf 10.1% gain in Wales) was bad enough the doubling of the differential proved a disaster. Indeed the whole Labour approach toward the regional list vote displayed a strategic and tactical ineptitude of astounding foolishness with astonishing consequences.
1) In the Scottish Parliament candidates are allowed to stand both for constituencies and for list seats. Due to historic dominance of FPTP results and a fairly general disdain toward list MPs Scottish Labour in general stood for one or the other – with the most able going for constituencies in general. In contrast SNP big hitters in general would stand for both.
2) The SNP’s message was “Vote for an SNP MSP in your constituency and for Alex Salmond for FM with your second vote”. In contrast Scottish Labour said nothing.
1) Scottish Labour lost a total of 7 seats in the election. However due to 1) above the stronger candidates in the FPTP element did not have an escape route on the lists. Thus Scottish Labour went from 44 seats to 37 seats but due to losing 20 constituencies and gaining 13 on the list the Parliamentary party is dominated by inexperienced newcomers.
2) The differential meant that Labour did not gain more seats in the regional lists to compensate for the constituency losses. If they had just maintained the differential at the 2007 level then another 4 seats (roughly !) would have come their way – perhaps depriving the SNP of a majority.
Data from the BBC and Wiki.