This is a completely different view of Billboard's Weekly USA Hit Parade. It is a MONTHLY view of the 10 most popular hits in the USA from 1959 through to 1981. I have made a point of NOT repeating any song no matter how long it stayed at #1 or any other position.
For instance let's take Bobby Darin's 'Mack the knife' which was #1 for 9 weeks in 1959, making up October, November and the 1st week in December. Instead of having 'Mack the knife' as #1 in both October and November, I only included it as #1 in October and found a #2 to become #1 in November. Is it right? Probably not, but what matters is that one has 120 hits a year which gives one a comprehensive look for that year.
This is not a strength or endurance competition. It doesn't matter if a song was 8 weeks at #1 but that the song was the best seller during a particular time. It is a list where one can find that a particular song was a hit at a particular time and had such and such as 'companions'. It was designed to give a 'snapshop' of a particular time without endless repetitions.
Bobby Lewis' 'Tossin' and turnin' was #1 for 7 weeks spanning July and August 1961. It suffices to know 'Tossin' and turnin' was #1 in July 1961. As everyone knows that a 'regular' hit would play for 8 to 10 weeks on the air waves it is easy to figure it out.