New firms are often based on ideas that the founders developed while working for incumbent firms. We study the macroeconomic effects of spinoffs through a growth model of product variety expansion, driven by firm entry, and product innovation. Spinoffs stem from conflicts of interest between incumbent firms' share holders and employees. The analysis suggests that incumbents invest more in product innovation when knowledge protection is stronger. An inverted-U shape relationship emerges, however, between the intensity of spinoff activities and the strength of the rul e of law. A calibration experiment indicates that, with a good rule of law, loosening knowledge protection by 53 reduces product innovation by one fifth in the short run and one seventh in the long run, but boosts the spinoff rate by one tenth and one sixt h in the short and long run, respectively. Nevertheless, per capita income growth drops and welfare deteriorates. The trade-offs are broadly consistent with evidence from Italian firms.