William Petty - Statistician

Statistician

Petty's only statistical technique is the use of simple averages. He would not be a statistician by today's standards but during his time a statistician was merely one that employed the use of quantitative data. Because obtaining census data was difficult, if not impossible, especially for Ireland, he applied methods of estimation. The way in which he would estimate the population would be to start with estimating the population of London. He would do this by either estimating it by exports or by deaths. His method of using exports is by considering that a 30 percent increase in exports corresponds to a similar proportionate increase in population. The way he would use deaths would be by multiplying the number of deaths by 30 – estimating that one out of thirty people die each year. To obtain the population of all of England he would multiply the population of London by 8. Such a simple use of estimation could have easily have been abused and Petty was accused more than once of doctoring the figures for the Crown. (Henry Spiegel)