A new interpretation of known facts: The case of two-way causality between trading and volatility

Efficient price setting implies that news create volatility since traders flock to the market in order to re-optimise their portfolios. In due course of the price finding process volatility should decline once the asset price approaches its new, efficient level. In this note I present evidence that the reverse mechanism plays as well. Traders genuinely increase volatility challenging the presumption that more traders help to identify the efficient price more quickly.