Genealogists need to be aware of the relative occurrence of the surnames they are researching. The number of people in the area where you are doing research with the same or similar surname increases the possibility that you will make a mistake in selecting a person with the same name as your target ancestor. The United States Census Bureau compiles a list of the most common surnames in the United States. If your ancestors' surnames show up on the list, I suspect that you are already aware of the challenges. Here is the list of the 15 most common surnames:
[Source: U.S. Census Bureau]
There are some other interesting facts illustrated by this list. in 1990 there were no Hispanic sunames in the top 15. Today, there are six. But it also likely that the top three will not be displaced for a long time.