By altering the turnout decision calculus, compulsory voting should alter the character of the voting population. Employing survey data across countries and Swiss cantons, I examine how the turnout decision calculus varies across voluntary and compulsory voting systems. Results indicate that many of the demographic, socio-economic and political factors known to correlate with turnout play a relatively weak role in motivating electoral participation where voting is mandatory. Thus, voting populations should be more reflective of the entire electorate in countries with compulsory voting. I conclude with a discussion of the potential implications of my findings.