Oil output is plunging because of the inefficiencies of Pemex, the giant state oil monopoly.

Converting one-fifth of Japan's unused farmland to solar would generate 50 gigawatts, he says, which is equivalent to the peak output of TEPCO, Japan's largest electricity firm (and a quasi-monopoly).

Taxation of monopoly is an alternative to regulation. it simply captures monopoly profit without affecting price or output.