On Floating Voters

And Predicting the 2019 Sri Lankan Presidential Election

Like many countries, two parties dominate Sri Lankan politics: The UNP (the Greens) and the SLFP (the Blues), or one of their modern incarnations.

And like in many countries, many people always vote for one party, and never for the other. These base voters form each party’s “voter base”. A chunk of votes that are virtually guaranteed.

The remaining “floating voters” could vote for either party. This latter block usually ends-up deciding the outcome of the election.

In this article, I do an approximate estimation of the base votes for the Blue and Green parties, and the floating vote, and analyse some implications.

Parenthesis: Some methodological details

An exact measure of the “base vote” would require per-voter data; each ballot would have to be tagged with the voter’s ID. Since presidential elections are by secret ballot, we don’t have this data. Thus, we have to resort to an approximation (see below for details). This approximation could be an over-estimate (because our estimate might include non-base-voters) or an under-estimate (because some base voters would not have voted in our sample elections).

We’ve restricted our analysis to the last four elections (1999, 2005, 2010 and 2015). The electorate and political views change over time, and 20 years seemed an arbitrary, but reasonable window.