The Four Seasons (or the 4 Seasons, as they were numerically billed in their heyday) were among the most successful pop singles artists of the rock era. With 46 hits on the Billboard Hot 100 between 1962 and 1995, they were ranked by chart researcher Joel Whitburn as 31st among the top singles acts of the period 1955-2006, and with 39 of those records having charted during the 1960s alone, Whitburn put them in sixth place for that decade. These statistics actually understate the group's chart achievements, however. Since lead singer Frankie Valli maintained a concurrent solo career often using the same songwriters and producers who worked with his band, and since his recordings are usually included with the group's on compilation albums, it is appropriate to factor his chart figures in as well. By that measure, Valli and the Four Seasons taken together were the fourth most successful pop singles act of the '60s, behind only the Beatles, Elvis Presley, and (trailing by a mere 15 points) Ray Charles, and 13th for the 51-year period, ahead of all other American groups.