The size of Ancestry.com’s record collection is a fascinating topic. As of June 2009, subscribers to Ancestry.com and our international sites can search the historical censuses for the U.S., UK and Canada, U.S. and international vital records, amazing collections of military and immigration records, and many others, not to mention the 10 million family trees added to our site by members in the last three years with over one billion profiles (names) and 20 million user-submitted photos and stories. This much is certain: Ancestry.com is far and away the largest collection of family history records online.

Defining and counting records on Ancestry.com

The concept of ‘counting’ records sounds relatively simple until you get deep into the details. How is a record defined? Is it a mention of a person? A household? A page? If a birth record has the person, parents, doctor and witness, how many records is that? And what of records where we don’t know for certain how many people are referenced, such as newspapers or city directories?

For our ‘fielded’ or indexed collections – structured data such as censuses and passenger lists – a record count is defined as the information about each specific person included. For example, one WWI Draft Registration Card is counted as one record. Similarly, each line on a census page is also counted as one record as typically it to will contain information about a specific individual.

For our ‘unfielded‘ collections such as newspapers and family histories, there is no underlying structure to define a field and so until now pages have been sampled then an average applied to determine an estimated name count. For example, our 42.5 million (countable) newspaper pages were multiplied by 60 names per page to achieve an estimated total name count.

Traditionally, we have counted our total number of records by combining the number of records for each person contained in our fielded collections and the estimated number of names in our unfielded collections.

However, as our company and collections have grown so significantly in recent years, we have decided to apply a new and highly conservative counting methodology that better reflects our differing data structures. Going forward, all unfielded pages will now be counted as one record – no name estimates will be included in our total record counts.

So what does this mean?

Based on this new methodology we have over 4 billion records. Previously, we referred to an estimated 8 billion names listed with in our record collections. This is a change to our counting methodology only – no records have been removed. Ancestry.com members will continue to have access to all the great records they had previously.

With new records launching every week, these numbers are always increasing. More importantly, no matter how we count them, our goal is to continue to bring millions of valuable records to our members like we’ve been doing for more than a decade.