Civil registration began for all events in all counties in 1864, and for all non-Catholic marriages in 1845. Griffith's Valuation, a property survey showing both occupiers and landlords between 1848 and 1864, has been filmed and indexed. Probate became the business of the secular court system in 1858. Although the wills were lost in the 1922 fire, the calendars of wills and letters of administration are available for study. These sources provide name, place, and date information.
Relationships appear in birth and marriage records and sometimes in probate calendars.
A census enumeration gathers data for statistical analysis. The reports generated from the data in the censuses of Ireland were subsequently published, and are available for study. The questions asked were included for a reason, and the resulting numbers influenced the government officials of the day, and the social and economic historians of more recent times. Genealogists also have something to learn from the statistics-details that enhance and encourage understanding. Historians have looked at the census statistics and used them to support various theories about the population of Ireland, when it peaked, and the impact of the potato famine.