We present a theory of entry through spinoffs where workers generate ideas and possess private information concerning their quality. Because quality is privately observed, adverse selection implies that the market can only offer a price that reflects the average quality of ideas sold. Only workers with good ideas decide to spin off, whereas workers with mediocre ideas sell them. Existing firms pay a price for ideas sold in the market that implies zero expected profits. Hence, firms’ project selection is independent of firm size, which can lead to scale-independent growth. This mechanism results in invariant firm-size distributions that resemble the data.