An essential function of securities markets is to discover asset values. The
function is critical for an efficient allocation of capital in the economy, as
better price discovery in the stock market translates into better capital
allocation decisions. For this reason, regulators and academics often see the
maximisation of price discovery as an extremely important goal. Market design
depends in large part on the decisions of stock exchanges and stock exchanges
themselves are now for-profit firms. Their income derives from trading revenues
and increasingly from the sale of information on prices. In this paper, we show
that the efficiency of price discovery is, among other factors, determined by
the fee charged by exchanges for price information.