Hertfordshire has a very comprehensive set of Militia lists from the period 1757 to 1801. These record the names of the men in the parish who were liable to serve in the County militia, and is in effect a census of most of the adult males between the ages of 18 and 45.
The list did not include those who had already served, and peers, clergymen, teachers, magistrates, apprentices, soldiers, seamen and constables were not eligible. Those who were infirm, or had a large number of dependents could be granted exemptions. The lists sometimes contain occupation, family and infirmity information.
Further information on the Hertfordshire holdings of militia lists at HALS is given in the book Tracing Your Family History in Hertfordshire. The Hertfordshire Family History Society has produced excellent booklets and these are now available on CD as Hertfordshjire Militia Ballot Lists.
Militia lists have proved useful on the following pages:
If you can add to the information given above tell me.