One of the major themes of my academic work is that modern democracies suffer from a serious problem of political ignorance (see, e.g., here and here). Most voters are “rationally ignorant.” Because there is so little chance that any one vote is going to be decisive in an election, individual voters have almost no incentive to learn about the competing parties and their policies, and as a result it is rational for them to devote very little effort to acquiring political knowledge (except for the few who have reasons for doing so unrelated to improving the “quality” of their votes).
In a proportional representation (PR) system such as that in Israel, the problem may be even worse than in the US. Voters in a PR system need to know not only what the policy differences between the parties are, but also what effect voting for a particular party will have on the resulting coalition government that emerges from an election. In some cases, voting for a right-wing party might actually increase the chance of creating a more left-wing coalition government or vice versa.
Yesterday’s Israeli election is a good example of this. In order to form a government, Israeli politicians must put together a coalition with at least 61 seats in the 120 seat parliament. Yesterday, the centrist Kadima Party got 28 seats, while right-wing parties (Likud, NU-NPR, Yisrael Beteinu) got 32, and parties to the left of Kadima got 31 (Labor 20, Meretz 4, Pensioner’s Party 7). Various special interest parties, got most of the remaining seats. Kadima is unlikely to form a coalition with the right-wing parties because these parties oppose Kadima’s central policy agenda: unilateral withdrawal from large parts of the West Bank. But because Kadima got only 28 seats, they will almost certainly have to form a coalition with the Labor Party (20) and perhaps other leftist parties as well. Had more right-wing voters picked Kadima rather than the parties closer to their views, Kadima might have won enough seats (say 40) to be able to form a government without Labor (which many Kadima leaders would have preferred to do), and therefore a government that would be less leftist.
Ironically, by voting for right-wing parties instead of Kadima, Israeli rightists may well have ensured a more left-wing government than would have resulted from their voting for Kadima instead! They “achieved” the opposite result from the one they probably intended. I suspect that this occurred at least in part because Israeli right-wing voters (like most other voters in PR systems) simply had insufficient incentive to put in the time necessary to think systematically about the impact of picking a particular party on the resulting coalition.
The extra knowledge burden imposed by the need to calculate coalition possibilities is an important (and generally ignored) weakness of PR electoral systems.