I’ve been scraping voting records for the 16th parliament (lower chamber only). That’s part of my continued (quixotic) interest in trying to get credible ideal point estimates out of situations (western European parliaments) where the assumptions of most estimation techniques (i.e., legislators vote sincerely) are violated.

There’s an article coming out by Luigi Curini and Francesco Zucchini (Italy:Government alternation and legislative agenda setting. In: Bjorn-Erik Rasch and George Tsebelis (eds.) The Role Of Governments in Legislative Agenda Setting) which assumes that ideal points can be estimated by only using final votes on bills.

Now, that works for previous parliaments — and I though I’d test that on the current parliament. The current parliament is interesting largely because of one opposition party — Italia dei Valori — which is centrist in its economic policy, and on many other issues, but is vociferously opposed to Berlusconi. So, it tends to oppose whatever it sees as compromise. As you can see from the graph, that pulls them to roughly the same position as the Partito Democratico.

Ideal points from the 16th Camera

What you can’t see from the graph is that the median Italia dei Valori legislator is slightly to the left of the Partito Democratico. That’s not the result you would expect if legislative rollcalls were determined by left-right positions instead of government-opposition. So, IMHO, we can’t get credible ideal points by restricting the analysis to final votes only.