We know that people have lived here since at least the Iron Age, but it is not until the Domesday Book of 1086 that we can get an idea of how many people lived in our parish.

The Domesday Book was ordered by King William the Conqueror to find out just what he had conquered and how much was owed him. For Hartley the book lists 9 villeins (better off farmers), 6 cottars (poorer farmers) and 3 slaves. The usual assumption is that all the slaves are listed, but only heads of households for the cottars and bordars. Scholars suggest a multiplier of 4 for these people, using this the population in 1086 would be about 63.

Throughout England the population continued to grow, reaching a peak shortly after 1300. It is probable that more people lived in Hartley then, than at any time since up to the 19th century. The Black Death, which arrived in England in 1348, and returned twice in the 1360s is thought to have carried off up to half of the population. If this is true for Hartley then around 200 people lived here in the first half of the 14th century, a number it would not reach again until the 19th century..

In 1377 the authorities introduced a poll tax of 4d (1p) per head of all adults over the age of 14. In Hartley 53 people paid the tax. Allowing for evasion (40%) and children (40%), it would seem that around 90 people were now living here.

Henceforth there are no reliable population figures for Hartley until the 17th century, but nationally the population continued to fall until the 1480s. The next big upswing was the century from 1540, when the population nearly doubled nationally to 5 million. However Hartley's population appears to have been largely static. For we have three separate sources for the 17th century, all of which point to around 90-100 people living in the parish. In 1664 there were 21 households which paid the Hearth Tax, making a population of about 90 based on the average size of household of 4.3 then. Two years later the poll tax was tried again, and Hartley paid 109 shillings. Most people paid a tax of 1 shilling (5p) a head, but a few paid more, so it is difficult to be certain, but it is indicative of over 100 people in Hartley. Finally in 1673 was the Compton Ecclesiastical Census, where each rector was asked to list the number of Anglicans, Roman Catholics and Non-Conformists (over the age of 16?) in their parish. In Hartley there were 71 Anglicans, which would again point to a number in the 90s overall.

The surviving parish registers for Hartley begin in the 18th century, and we can gain some estimate of the population from the baptism register. The national birth rate was about 35 per thousand, and while the figures below are clearly an inexact science they do show an upward drift of population in 18th century Hartley and the last quarter's figure is close to the census.

Finally we reach the era of the census and from now on we have accurate figures for Hartley's population every 10 years.

* Boundary changes, eg. top of Ash Road transferred to Hartley from Ash parish (1951 figure in brackets is what it would have been with the 1961 boundaries)
** Fawkham and Hartley ward