other (as in Laffont and Tirole 1993). So the Brown tax is indeed a tax, and one that reduces the incentive to mine. Next …, the ex post Resource Super Profits Tax (RSPT) falls on quasi-rents as well as on rents, and therefore involves some …. Fourth, the successor to the RSPT – the Minerals Resource Rent Tax (MRRT) – has many of the inefficiencies of the RSPT but …