Since the civil rights movement of the 1950s and 1960s, and especially since the Civil Rights Act of 1968 prohibited racial discrimination concerning the sale, rental, and financing of housing, the number of sundown towns has decreased. However, as sociologist James Loewen writes in his book on the subject, it is impossible to precisely count the number of sundown towns at any given time, because most towns have not kept records of the ordinances or signs that marked the town's sundown status. His book, "Sundown Towns: A Hidden Dimension of American Racism", notes that hundreds of cities across America have been sundown towns at some point in their history.