sample) left-wing party increases the _sharegain_ of the bottom 60 percent of households by one percentage point.

# **6. Robustness:  Electoral institutions, middle class coalitions and leader tenure**

Table 4 presents several specifications that demonstrate the robustness of the party and party age results to controls for numerous other political mechanisms of redistribution. The first two columns control for the mechanism advanced by Iversen and Soskice (2006), that electoral laws influence the incentives of the middle and poor classes to ally with one another in the pursuit of redistribution away from the rich. This mechanism therefore raises the possibility that our results on the partisan and age characteristics of the governing party are spuriously influenced by the omission of controls for the electoral and political institutions of countries.

The first two columns in Table 4 address this issue by including three variables from the Database of Political Institutions: whether elections are governed by proportional or plurality rules, which directly address the issues raised by Iversen and Soskice; the mean district magnitude of the electoral districts of the lower legislative chamber; and whether the political system is presidential, parliamentary or semi-presidential.

Even controlling for these variables, left-wing parties continue to redistribute significantly more, an effect that is, as before, significantly attenuated in older left-wing parties. Of the new political variables, neither district magnitude nor political system is significant. The electoral system variable is large and significant, but in the direction opposite to that predicted by Iversen and Soskice (2006). Unique characteristics of the sample are likely to account for this.

Iversen and Soskice (2006) present evidence from a sample of advanced industrial democracies that proportional electoral systems exhibit greater redistribution. Our estimates all employ country fixed effects, so effects are identified only from those countries that exhibit a change in electoral rules. There are only two in our sample, El Salvador and Bolivia. In these two countries, quite different from those analyzed by Iversen and Soskice, the effects of electoral rules appear to go in the other direction: the post-redistribution share (more exactly, the _sharegain_ ) of the bottom quintile is significantly higher in plurality systems and the share of the top quintile is significantly lower. These results – only illustrative, given data paucity – reinforce the recommendation of Iversen and Soskice to explore more deeply the dynamics of redistribution in poorer countries.

Columns three and four account for the arguments made by Lupu and Pontusson (2011), that redistribution is driven by whether the income shares of the middle class are closer to those of the poor (promoting coalition-building with the poor against the rich) or to those of the rich. The partisan effects remain highly significant in these regressions: left-wing parties redistribute more, but the effect is attenuated among older parties.

Consistent with the arguments that Lupu and Pontusson, the lower is the ratio of middle to lower income quintiles (the closer together are the two quintiles), the higher is the _sharegain_ of the bottom quintile and the lower is the _sharegain_ of the top quintile. Though these effects are not significant, the other ratio, top-to-middle, has a significant effect in both cases: the lower the ratio of the top to middle income quintiles (the closer is the middle class to the rich), the higher is the _sharegain_ of the top quintile and the lower is the _sharegain_ of the bottom quintile.

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