An Order of Merit was introduced for the 1975/1976 season, which saw Ray Reardon ranked in the top position. This system was only in place for a season before being replaced by the world rankings, which saw successive periods of dominance for the first 22 seasons by Ray Reardon (1976/1977–1982/1983), Steve Davis (1983/1984–1989/1990) and Stephen Hendry (1990/1991–1997/1998), interrupted only by the 1981/1982 season when Cliff Thorburn held the position. The following period (1998/1999–2009/2010) was shared by O'Sullivan (five seasons), John Higgins (three seasons) and Williams (three seasons), while Hendry regained the position for the 2006/2007 season, ensuring that the four men held the position between them for a twenty-year span (1990–2010). In the first 34 years of the world rankings, only seven players held the number-one position.
This period of dominance ended with the restructuring of the rankings system for the 2010/2011 season, which saw the world rankings updated after each tournament carrying ranking points, rather than just once a year after the World Championship as under the previous system. Since the introduction of the new system, John Higgins, Neil Robertson, Mark Williams, Mark Selby and Judd Trump have all attained the number-one rank. Robertson and Trump assumed and lost the position mid-season, so neither would have been officially ranked number one under the previous system.
Sometimes other factors besides performance in ranking events impact upon the rankings. Alex Higgins would have been ranked number 1 in 1982/1983, but had ranking points deducted as a result of disciplinary action, and similarly, Robertson assumed the number-one spot earlier than would have been possible if John Higgins hadn't received a six month ban in 2010. Higgins would also have finished the 2010/2011 season ranked number 1 if he weren't banned, since the points he was guaranteed from participating in the tournaments he missed would have been enough for him to take the top spot, and similarly O'Sullivan's decision not to enter the Malta Cup during the 2005/2006 season cost him the top rank for the following season, since the entry points on offer would have been enough for him to retain the position.
Stephen Hendry holds the record for most seasons at number one, with nine seasons (1990/1991–1997/1998 and again in 2006/2007). His first spell of eight consecutive seasons in this position is also a record.
It took both Steve Davis and Stephen Hendry just five seasons from turning professional to reach the number 1 rank.
a Even though the "official" rankings started in 1976, an Order of Merit was published in 1975 to determine the seedings for events. It used the same criteria that was used to determine the first set of official rankings the following year.