The ATP Rankings are the Association of Tennis Professionals' (ATP) merit-based method for determining the rankings in men's tennis. The top-ranked player is the player who, over the previous 52 weeks, has garnered the most ATP ranking points. Points are awarded based on how far a player advances in tournaments and the category of those tournaments. The ATP has used a computerized system for determining the rankings since 23 August 1973. Since 1979 an updated rankings list is released at the beginning of each week.
Since 1973, 25 men have been ranked number 1 by the ATP.Pete Sampras holds the record for the most year-end number 1 (six, all consecutive).Roger Federer holds the records for the most total weeks at number 1 (302) and most consecutive weeks at number 1 (237). Two players, Ivan Lendl and Marcelo Ríos, have reached number 1 without previously having won a Grand Slam tournament. Lendl reached number 1 on February 21, 1983, but did not win his first Grand Slam title until the 1984 French Open. Rios reached number 1 on March 30, 1998 and is the only number 1 player who never won a Grand Slam singles title.Patrick Rafter spent the fewest weeks at number 1 (one week). Lleyton Hewitt is both the youngest world number 1 (20 years, 268 days) and youngest year-end number 1, while Ivan Lendl is the oldest year-end number 1 (29 years, 299 days). Andre Agassi is the oldest number 1 (33 years, 131 days).
Since 1973 when the ATP ranking started, there have been eleven years when one player held the top spot for the entire year. In contrast, 1999 had the most number 1 players of any year since the rankings started. There were five players who were number 1 sometime during that year - Sampras, Moya, Kafelnikov, Agassi and Rafter.
Since the introduction of the ATP rankings the method used to calculate a player's ranking points has changed several times. As of 2011, the rankings are calculated by totaling the points a player wins in his best eighteen tournaments, subject to certain restrictions. For top players the counting tournaments are the four Grand Slam tournaments, the eight mandatory ATP World Tour Masters 1000 tournaments, the player's best four eligible ATP World Tour 500 series tournaments (the non-mandatory ATP Masters 1000 event in Monte Carlo may be substituted for one of these), and his best two results from ATP World Tour 250 series. Lower-ranked players who are not eligible for some or all of the top tournaments may include additional ATP 500 and ATP 250 events, and also ATP Challenger Series, and Futures Series tournaments. The ranking points of players who qualify for the year-end ATP World Tour Finals also include any points gained at that tournament, increasing their counting tournament total to nineteen.
The ATP year-end no. 1 ranked player is determined as the player at the head of the ATP rankings following the completion of the final tournament of the calendar year, usually in November or December. Pete Sampras holds the record of six year-end no. 1 rankings, which were in consecutive years from 1993 through 1998.
Only six players have stayed at ATP no. 1 in the rankings every week of a calendar year. Federer is the only player to have been ranked no. 1 every week for three consecutive calendar years.
Time as year-end number 1/Total times as year-end number 1
Ranked number 1 during every week of the calendar year
John McEnroe finished the year as the no. 1-ranked player for four consecutive years from 1981 to 1984.
Lleyton Hewitt at age 20 became the youngest male player to hold the world no. 1 ranking. He obtained this in November 2001.
^Buddell, James (July 16, 2012). "Federer Rises Above". London: ATP World Tour. Retrieved July 16, 2012. Andre Agassi, who remains the oldest player to have been No. 1 in the South African Airways ATP Rankings, at 33 years and 131 days in 2003, proved to be a great inspiration.
^ abcdefghi"Hewitt jubilant as world's No. 1". The Age. November 15, 2002. Retrieved September 6, 2012. Only five other players – Stefan Edberg (1990–91), Ivan Lendl (1985–87), John McEnroe (1981–84), Bjorn Borg (1979–80) and Jimmy Connors (1974–78) – have achieved the mighty feat.
^ abcFord, Bonnie D. (April 9, 2010). "Tennis still imbued in Lendl's blood". ESPN. ESPN Internet Ventures. Retrieved September 6, 2012. In 1988, [Wilander] won a five-set endurance contest, breaking a six-match losing streak to Lendl. The win interrupted Lendl's three-year reign as world No. 1...
^Wilansky, Matt (August 31, 2006). "Inside the numbers". ESPN. ESPN Internet Ventures. Retrieved September 5, 2012. [I]n 1999 he won the French Open title, the only major that had eluded him. He finished the year ranked No. 1 in the world for the first and only time in his career.