I cannot find a specific person I thought was born in a certain country. Why is this?

In order to maintain consistency, the Shoah Foundation uses cataloguing guidelines based on time periods. Some countries' borders and names changed after World War I and again after World War II. To keep the information in the archive historically accurate, the date of birth determines the country name catalogued for the country of birth. Example: If a survivor states that he was born in Vienna in 1909, the country of birth is indexed as Austria-Hungary. Austria came into existence only after World War I.