I present a theory of development in which heterogeneously talented entrepreneurs require credit to start new projects and open new sectors. During development the variety of sectors expands, which allows better sorting of entrepreneurial talent. The paper shows that, in addition to increasing the average productivity of matches between agents and sectors, this process also mitigates informational frictions in the financial markets. Furthermore, the impact of sectoral variety on the operation of financial markets gives rise to an interesting feedback between financial development and R&D effort, which may lead to different types of dynamics. A successful economy exhibits a progressive increase in the variety of sectors, which in turn enhanc...