In this article I contend that “winner-take-all markets” (i.e., those where slight differences in performance mean huge differences in income) do not respect the libertarian principle that individuals are entitled to the fruits of their labour. If income must reflect the fruits of one’s labour (which must itself be measured by performance), then income in these markets is much higher than the fruits of the labour – which, on this principle, justifies the adoption of a very progressive tax system.