In a seminal work by Gurley and Shaw, they established that economic development is typically accompanied by a transition from self-financed to intermediated investment. This work seeks to analyse the co-evolution of the real and financial sectors during this growth process. We study the biases generally observed in the AR(1) OLS estimation, and apply the result of these to causality tests between finance and growth. As originally identified by Sawa these biases are present in regressions using small samples, while OLS will normally be consistent if the error term is i.i.d. We assess and find analytical expressions for these biases. The phase-average methodology has been often used to study the growth effect of financial deepening; notably ...