GRAUNT AND THE SCIENCE OF STATISTICS.
As statistical writing Graunt's "Observations upon the Bills of Mortality" are superior to any of Petty's works. Indeed they alone can claim to be "statistics"; Petty's "Essays" are so different in character that his own name of "political arithmetick" is still their most accurate description. The difference, as has been pointed out[1], arises in part rather from Graunt's sparing use of calculation than from any especial merit in such calculations as he does make. His estimate of London's population[2] is superior to Petty's in no way unless it be by reason of priority; and his table of mortality is as pure guess work as anything that Petty ever wrote[3]. But the difference between them cannot be wholly explained by the circumstance that Graunt's temptation to reckon was less than Petty's because his data were more complete. The spirit of their work is often different when no question of calculation enters. Petty sometimes appears to be seeking figures that will support a conclusion which he has already reached: Graunt uses his numerical data as a basis for conclusions, declining to go beyond them[4]. He is thus a more careful statistician than Petty, but he is not an economist at all.
Some of the most important facts which the study of vital statistics has yet discovered were first brought to light by Graunt. Though they may be read at length in his "Observations" here reprinted, it is essential to an adequate appreciation of his merits that the more pregnant of his discoveries be brought together by way of summary. Four are particularly noteworthy. In the first place, the regularity of certain social phenomena which appear to
