Finding Effects of Sequential Housing Price Control Policies Using Various Forms of Difference in Differences

Various forms of housing price and rent control policies are implemented in many countries, and finding their impacts is an important issue. Over 2019-2023, the South Korean government announced a policy to put a ceiling on housing prices in some regions of Seoul, and then subsequently implemented, strengthened, weakened, and finally abolished the policy. This is a rather complicated scenario for a policy, and the goal of this paper is to assess the effects of the policy and its changes with difference in differences (DD). We establish a detailed DD-analysis protocol, employing diverse forms of DD. Applying the protocol where a systematic difference in the untreated outcome trajectories of the treated and control groups is allowed, we assess the policy impacts. We find that, despite the active involvement of the government in the housing market, the overall effect is about a 4-5% decline in housing prices in Seoul.