Piketty's Law

Observation that wealth in a market economy, absent government intervention, will tend to accrue upwards into a handful of dynastic fortunes because the rate at which the rich can make money exceeds the rate at which the aggregate wealth in the economy grows. ("The best way to make a large fortune is to start with a small one", as the saying goes.)

Scheidel's Corollary states that once this sort of inequality exists it is permanent unless and until the economy faces a disruptive external event such as a war, since the now-entrenched wealthy elite can use their political influence to block attempts at internal reform.