William Petty,
The Economic Writings of Sir William Petty…
(1899)
“ In other words he pursued the method of political arithmetic as distinguished from statistics. Statistics demands enumeration. The validity of its inferences depends upon the theory of probabilities as expressed in the Law of Large Numbers. Therefore it adds, it does not multiply. Political arithmetic, as exemplified by Petty, multiplies freely; and the value of its results varies according to the nature of the terms multiplied. For example, in the absence of a census Petty had to calculate the population of London, of England, and of Ireland. ”
