The old link appears to be password protected when the referrer is not Google or another page on the same site. You can get to the article via a table of contents, see ‘The Limits of Instrumental Rationality in Social Explanation’ by Doug Mann.

Anyway the simple distinction between instrumental returns and expressive returns is that the former are obtained by achieving one’s ends (usually in a narrow sense, i.e., financial gain or pleasure) while the latter are obtained by engaging in some kind of expression, which in the case of voting is clearly decoupled from the outcome of the overall vote, as the individual voter is never decisive.

An example of the distinction would be voting for a transfer program because you expect to be a recipient of the transfer (instrumental) versus voting for a transfer program because doing so expresses that you care (expressive).

I’m interested because I’m writing an article on ‘comparison systems’ which discusses the differences between representational voting, decision voting, polling, ranking, and rating.