I tested Bertrand's 1887 ballot formula on 648 vote splits and the answer was always (p-q)/(p+q).

Part 100 of Forgotten Theories, a series re-testing old scientific claims with modern tools. Find the rest under the #forgotten-theories tag. In 1887 Joseph Bertrand sent a four-page note to the Comptes Rendus of the French Academy. The question he ...