Complex sentence: As of 2006, roughly 12% -14% of the U.S. population was foreign born, this is attributed to legal immigration from around the world and illegal immigration from adjacent countries, such as Cuba and Mexico.
Split into simpler sentences: As of 2006, roughly 12% -14% of the U.S. population was foreign born. This is attributed to legal immigration from around the world and illegal immigration from adjacent countries, such as Cuba and Mexico.