Figure 8.2 presents the estimated effects of seat shares on box scores under different ballot access rules in a multivariate context. To generate these results I used the following approach. First, I performed a logit transformation of my dependent variable, the proportion of bills initiated by a chief executive and approved by the legislature of his or her respective country. Next, I regressed these box scores on a series of explanatory variables using ordinary least squares (OLS). The following explanatory variables are considered:

Presidential, Mixed, and Non-Westminster Parliamentary. Each of these variables takes the value of 1 if the country has the referred constitutional structure, and 0 otherwise. Constitutional structures were classified according to the criteria developed by Cheibub (2007). The following countries were coded as Westminster-style systems: Canada, Bangladesh, Ireland, Malta, United Kingdom, and New Zealand.

Coalition Government. This is a binary indicator that takes the value of 1 if the government is a multiparty coalition, and 0 otherwise. A government is considered to be a multiparty coalition if two or more political parties represented in the national legislature hold cabinet positions. Source: Cheibub et al. (2004) and the author's own calculations.