This paper evaluates the empirical relationship between the level of financial intermediary development and (i) economic growth, (ii) total factor productivity growth, (iii) physical capital accumulation, and (iv) private saving rates. We use (a) a pure cross-country instrumental variable estimator to extract the exogenous component of financial intermediary development, and (b) a new panel technique that controls for biases associated to simultaneity and unobserved country-specific effects. After controlling for these potential biases, we find that (1) financial intermediaries exert a large, positive impact on total factor productivity growth, which feeds through to overall GDP growth; and (2) the long-run links between financial intermediary development and both physical capital growth and private saving rates are tenuous.