Must have been a slow day at the HBR. What evidence is there that a startup's founders age is a determinate of success? What does it mean to be successful in

Must have been a slow day at the HBR. What evidence is there that a startup's founders age is a determinate of success? What does it mean to be successful in this context? in general? What other properties of a startup founder might contribute to the startup's success? How are those properties related to her/his age.