How does portfolio of long-term investors like pension funds change relative to the stated strategic portfolio? We investigate their portfolio dynamics using an international database that spans over 20 years and focus on portfolio rebalancing. We find that a significant proportion of the change in the weight of equity is related to passive change in portfolio due to realized equity returns. Moreover, pension funds follow asymmetric rebalancing, they rebalance poorly when stock market is doing well but rebalance strongly when stock market is doing poorly. Actual change in equity portfolio only partially reflects strategic changes. We also study cross-sectional differences in rebalancing. The results indicate that US and defined benefit pension funds rebalance less. Moreover, external managers and active managers can be identified as the major source of poor rebalancing. Lastly, between asset classes, pension fund are more passive in alternative investments.