The speed with which stock markets adjust to information and news flow into asset prices is of importance to investors, regulators and policymakers. In this article, we provide a simple and uniform empirical framework involving the use of a volatility measure to compare the speeds of adjustment in index prices in response to all available market information. The stock indices of 23 major emerging economies are compared with 10 mature stock indices from developed countries with reference to the speed of their price adjustments. We find that the index prices of developed countries adjust faster when compared to those of emerging countries. Our findings are independent of any GARCH specification and are also robust to potential mistakes in the model specification because we make use of a fully empirical bootstrap procedure to compute the standard errors. We also rank the countries in terms of the speed of index price adjustment. The results show that the random walk effect is generic and exists in all price indices.