Oh, I had no idea that it was that low. I'd though most of europe used compulsory voting.

Although, according to the wikipedia article, there are an additional 21 countries that have compulsory voting but don't enforce it. Which suggests that there are at least 2 billion people who live in a system with some sort of compulsory voting, and a bit under 400 million have enforced compulsory voting (I checked the populations of some of the countries).

(For what it's worth, I'm in Australia (with compulsory voting), so that would have contributed to my reaction.)