Does reporting quality affect systematic risk? Evidence from a regulatory lottery

On June 1, 1976, the Swedish parliament voted on a legislative bill that, if approved, would have substantially increased the quality of the corporate information disclosed to the public. Since parliament was hung, the outcome of the vote was decided by a lottery. The winning lottery ticket was a "No", which meant that the bill was rejected. I exploit this lottery as an exogenous event to study if reporting quality affects systematic risk. I find that the rejection of the bill resulted in a negative abnormal return that persisted in the following day. This result suggests that there is a causal relationship between reporting quality and equity prices through its impact on systematic risk.