The following graph shows all the leaders of the Labour Party who have been in post when the party has been in opposition at the time of at least one round of annual council elections.
For each of them, I have calculated the average share of the vote for the Labour Party in those rounds of local elections whilst in opposition in Parliament. The vote share calculations use the Thrasher & Rallings national vote share calculations, i.e. they are adjusted to allow for different wards being up for election each year. Therefore the different performance of different leaders isn’t due to which wards were up in the years they were in post – the figures are adjusted to cater for this.
And with that, here’s the data:
To see the full context of the predictions and results each year, see my PollBase collection of local election results.
UPDATE: In response to a query on Twitter from James Morris, here’s also a graph that shows their highest and lowest performance.
As you’ll have seen from the above graph, Jeremy Corbyn‘s average is the worst. What this additional graph also shows is that even the post-Corbyn surge, Corbyn is still performing poorly.
He has the worst average, the worst lowest score and also the worst highest score of any Labour opposition leader since this data started.