How Gap Measures Determine Results: The Case of Proportional Systems and the Gender Mobilization Gap

How scholars conceptualize and measure the gender gap in mobilization can have profound consequences for substantive conclusions. Scholars typically refer to a difference between women and men's turnout (difference-in-proportions measure) or a fraction of women voters among all voters (proportion measure). Using the case of proportional representation (PR) reform in Norway, I demonstrate that, in the context of low men's turnout, the proportion measure indicates that PR narrows the gap, while the difference-in-proportion measure indicates that it widens the gap. This is because mobilizing fewer women than men widens the difference between women and men's turnout, but may constitute a greater proportional increase in women's mobilization compared to men when only a few men (and even fewer women) vote. These findings bring together seemingly opposing arguments in the PR-gap debate and have wide implications for the study of ‘gaps’ within and beyond gender scholarship.