Yes, these are factors that we considered in another study that we conducted for Elections Canada a few years ago. Proxy voting, advance polling and postal voting are three measures that, taken together, increase voter turnout in the world the most. For the same sample as the one we used for this study, there was an impact of 11 percentage points. Those three measures taken together, in the countries where they were in existence, increased voter turnout considerably.
On November 22nd, 2007. See this statement in context.