Rallings/Thrasher have been collecting and commenting on byelections since the early 1980s. Following encouragement from Cris Derby, then editor of Local Government Chronicle, we began a regular column for the magazine in July 1983. More recently, we’ve written on this topic for Local Government First. We’ve also used these data to build the Sunday Times’ model for forecasting gains and losses in successive rounds of local elections.
We’re sure that there’s much more that can be done with these data and look forward to seeing what people do with them.

You can download the data file here and an explanatory note describing the variables here.

Some caveats. We have never stored the names of byelection candidates, just party, votes, turnout and the headline result. When we consolidated our databases in the late 1980s a number of by-elections got lost in the digital ether. Enthusiasts may want to try and track them down. There is a chance that some uncontested by-elections are also missing. We stopped collecting by-elections from Scotland after they moved to STV/AV for council elections. Turnout/Electorates were and still are hard to come by so exercise caution when using these data.

There will be errors in the file. Mistakes happen. Ward names may be incorrect. Party labels may be wrong – particularly when the Alliance was in full flight during the 1980s and were fighting as SDP/Lib or Lib/SDP. Cut us some slack, please. If you do use the file, and we sincerely hope you do, then please read the explanatory notes carefully before getting in touch with us – contact details on the front page.

Meanwhile, the Table below has details and summaries of by-elections conducted from May 2015. Each spreadsheet begins with by-elections held simultaneously with each year’s main May elections and ends the following April.