What about 2006 onwards?
Rating leaders January 1843- January 2005
These ratings are from chessmetrics.com.
John Cochrane: January-April 1843
Howard Staunton: May 1843-August 1849
Lionel Kieseritzky: September-November 1849, February 1850-September 1851
Henry Buckle: December 1849- January 1850
Tassilo von der Lasa: October 1851-December 1852
Daniel Harrwitz: January 1853-February 1856
Serafino Dubois: March 1856-August 1858
Paul Morphy: September 1858-November 1861
Adolf Anderrsen: December 1861-March 1862, June-August 1870
Louis Paulsen: April 1862-May 1865, July 1878
Berthold Suhle: June 1865-August 1866, October 1866-February 1867
William Steinitz: September 1866, March-June 1867, September 1870-July 1877, December 1882-June 1883, October 1883-January 1886, March 1886-May 1890
Ignatz Kolisch: July 1867-November 1868
Gustav Neumann: December 1868- May 1870
James Mason: August 1877-June 1878
they have him #Johannes Zukertort: August 1878-November 1882, July-September 1883, February 1886
Emmanuel Lasker: June 1890-December 1902, April 1907-April 1908, September 1908-July 1912, June 1914-April 1915, March 1916-March 1919, April 1924-December 1926
Harry Pillsbury: January 1903-April 1904
Jose Raul Capablanca: May 1914, May 1915-February 1916, April 1919-December 1923, March-October 1927, November 1928-April 1929, May-July 1937
Alexander Alekhine: January-March 1924, November 1927-October 1928, May 1929-December 1935, December 1937-October 1938, November 1942, April 1943-May 1944, July 1944
Efim Bogoljubow: January-February 1927
Max Euwe: January-August 1936, March-April 1937, August-November 1937
Mikhail Botvinnik: September 1936-February 1937, November 1938-September 1940, April 1941-October 1942, June 1944, August 1944-May 1950, December 1952-July 1953, April-May 1954, April-May 1958
Reuben Fine: October 1940-March 1941
Samuel Reshevsky: December 1942-March 1943, May-November 1952, August-October 1953
David Bronstein: June 1950-December 1951
Vassily Smyslov: January-April 1952, November 1953-March 1954, June 1954-March 1958, June-September 1958
Mikhail Tal: October 1958-April 1961, April-August 1965, June-July 1966
Tigran Petrosian: May 1961-January 1964
Bobby Fischer: February 1964-March 1965, September 1966-July 1974
Viktor Korchnoi: September-December 1965
Boris Spassky: January-May 1966, August 1966
Anatoly Karpov: August 1974-August 1982, November 1984-January 1985
Garry Kasparov: September 1982-October 1984, February 1985-October 2004
Viswanathan Anand: November 2004-January 2005
Chessmetrics is screwy ! You can take almost any player above and make a mockery of chessmetrics rating. Lets take Anderssen.
In 1851 he wins the first international chess tournament London 1851. In that tournament he beats Keizeritsky 4 to 1/2. He plays his immortal game against Keizeritsky that year. And yet chessmetrics places Keizeritsky at the top of the rating list? Screwy beyond comprehension.
Look at Pillsbury, they have him #1 in 1903 and 1904. These were not only the last few years of his career but among the last years of his life. In his last big tournament (Cambridge Springs 1904) he finished a dismal 8th with a minus score. And chessmetrics rates him as #1 in 03' and 04' ?
Check this rating list out---there are mistakes all over the place.
These ratings are from chessmetrics.com.
John Cochrane: January-April 1843
Howard Staunton: May 1843-August 1849
Lionel Kieseritzky: September-November 1849, February 1850-September 1851
Henry Buckle: December 1849- January 1850
Tassilo von der Lasa: October 1851-December 1852
Daniel Harrwitz: January 1853-February 1856
Serafino Dubois: March 1856-August 1858
Paul Morphy: September 1858-November 1861
Adolf Anderrsen: December 1861-March 1862, June-August 1870
Louis Paulsen: April 1862-May 1865, July 1878
Berthold Suhle: June 1865-August 1866, October 1866-February 1867
William Steinitz: September 1866, March-June 1867, September 1870-July 1877, December 1882-June 1883, October 1883-January 1886, March 1886-May 1890
Ignatz Kolisch: July 1867-November 1868
Gustav Neumann: December 1868- May 1870
James Mason: August 1877-June 1878
Johannes Zukertort: August 1878-November 1882, July-September 1883, February 1886
Emmanuel Lasker: June 1890-December 1902, April 1907-April 1908, September 1908-July 1912, June 1914-April 1915, March 1916-March 1919, April 1924-December 1926
Harry Pillsbury: January 1903-April 1904
Jose Raul Capablanca: May 1914, May 1915-February 1916, April 1919-December 1923, March-October 1927, November 1928-April 1929, May-July 1937
Alexander Alekhine: January-March 1924, November 1927-October 1928, May 1929-December 1935, December 1937-October 1938, November 1942, April 1943-May 1944, July 1944
Efim Bogoljubow: January-February 1927
Max Euwe: January-August 1936, March-April 1937, August-November 1937
Mikhail Botvinnik: September 1936-February 1937, November 1938-September 1940, April 1941-October 1942, June 1944, August 1944-May 1950, December 1952-July 1953, April-May 1954, April-May 1958
Reuben Fine: October 1940-March 1941
Samuel Reshevsky: December 1942-March 1943, May-November 1952, August-October 1953
David Bronstein: June 1950-December 1951
Vassily Smyslov: January-April 1952, November 1953-March 1954, June 1954-March 1958, June-September 1958
Mikhail Tal: October 1958-April 1961, April-August 1965, June-July 1966
Tigran Petrosian: May 1961-January 1964
Bobby Fischer: February 1964-March 1965, September 1966-July 1974
Viktor Korchnoi: September-December 1965
Boris Spassky: January-May 1966, August 1966
Anatoly Karpov: August 1974-August 1982, November 1984-January 1985
Garry Kasparov: September 1982-October 1984, February 1985-October 2004
Viswanathan Anand: November 2004-January 2005