1. If we are talking about really big companies there are a handful of examples anyhow. I am not sure if an empirical comparison is even possible.
2. I think there is a survivor bias here. Most of the biggest companies reach scale very quickly. The scale creates an incentive for the other co-founder to stick on. There is some anecdotal evidence to believe that if scale does not come early on - most likely there won't be a 'really big' company. If the co-founder quits and the founder soldiers on - it just adds another data point to pg's co-founder theory.
2. I think there is a survivor bias here. Most of the biggest companies reach scale very quickly. The scale creates an incentive for the other co-founder to stick on. There is some anecdotal evidence to believe that if scale does not come early on - most likely there won't be a 'really big' company. If the co-founder quits and the founder soldiers on - it just adds another data point to pg's co-founder theory.