Another factor is that older founders will have (relatively) less need of YC: they'll have their own funds, experience and contacts. The age-distribution of YC

Another factor is that older founders will have (relatively) less need of YC: they'll have their own funds, experience and contacts. The age-distribution of YC startup applicants affects the age-distribution of those that are funded, and so doesn't necessarily generalize to all startups. E.g. Adobe was founded by a couple of guys in their 40's.