When this project collapsed, he went to work for the dowager Lady Gerard at Sandon, Staffordshire as steward, auditor and secretary (1670–72).
These positions in the ceremonial branch of the state were lucrative and on three occasions he was sent abroad to confer the Order of the Garter on foreign princes.
"The first great economic statistician", as Richard Stone calls him,[4] came a generation after John Graunt and William Petty and continued their work.
Material from his manuscripts appeared in the writings of his friend Charles Davenant and—a century later—in Adam Smith's Wealth of Nations (Book I, Chapter VIII), and in An Estimate of the Comparative Strength of Britain by George Chalmers.
It describes the demographic characteristics of the population of England and Wales: age, gender, marital status, numbers of children, servants and "sojourners".
He calculated the increases in shipping (for war and trade), customs, coinage, buildings, fortresses, and the purchases and improvements of land.
The relevant passage runs: It is observed that but one-tenth the defect in the harvest may raise the price three-tenths, and when we have but half our crop of wheat, which now and then happens, the remainder is spun out by thrift and good management, and eked out by the use of other grain; but this will not do for above one year, and would be a small help in the succession of two or three unseasonable very destructive, in which many of the poorest sort perish, either for want of sufficient food or by unwholesome diet.
The Natural and Political Observations appear with some of King's unpublished writings in a volume edited by Peter Laslett.