Quick question: I am wondering what the industry "standard" is for pricing European options on single stocks. Since only American options on single stocks trade in the market, only American implied vols are available. My understanding is that the American implied vols are simply plugged into Black-Scholes to obtain European option prices, i.e. American implied vols are assumed equal to European implied vols. This procedure is then justified by the fact that American options are rarely exercised early.Does anyone know if this is indeed the industry standard or if there has been any work done on measuring the "error" from doing this? Is there a better way to obtain European options prices given their American implied vols? (I do realize it's possible to set up an optimization problem to back out local voatilities from the American option prices. The local vols could then be used to price the European options. Such an optimization problem would be difficult to implement in practice.)