Background: Theodore Ernest Els (; born 17 October 1969) is a South African professional golfer. A former World No. 1, he is known as "The Big Easy" due to his imposing physical stature (he stands 6 ft 3 in (1.91 m)) along with his fluid golf swing. Among his 71 career victories are four major championships: the U.S. Open in 1994 at Oakmont and in 1997 at Congressional, and The Open Championship in 2002 at Muirfield and in 2012 at Royal Lytham & St Annes. He is one of six golfers to twice win both the U.S. Open and The Open Championship.
Context: 2003 gave Els his first European Tour Order of Merit. Although playing fewer events than his competitors Els won four times and had three runners-up. He also performed well in the United States with back to back victories at the Mercedes Championship - where he set the all-time PGA Tour 72-hole record for most strokes under par at 31 under - and Sony Open and achieved top-20 spots in all four majors, including a fifth-place finish at the U.S Open and sixth-place finishes at both the Masters and PGA Championship. To top off the season Els won the World Match Play title for a record-tying fifth time. In 2003 he was voted 37th on the SABC3's Great South Africans.  2004 was another successful year as Els won 6 times on both tours, including big wins at Memorial, WGC-American Express Championship and his sixth World Match Play Championship, a new record. His success did not stop there. Els showed remarkable consistency in the Majors but lost to Phil Mickelson in the Masters when Mickelson birdied the 18th for the title, finished ninth in the U.S. Open after playing in the final group with friend and fellow countryman Retief Goosen and surprisingly lost in a playoff in the Open to the then unknown Todd Hamilton. Els had a 14-foot (4.3 m) putt for birdie on the final hole of regulation for the Open at Royal Troon, but he missed the putt and lost in the playoff. Els ended the major season with a fourth-place finish in the PGA Championship, where a three-putt on the 72nd hole would cost him a place in the playoff. In total, Els had 16 top-10 finishes, a second European Order of Merit title in succession and a second-place finish on the United States money list.  2004 was the start of the "Big Five Era", which is used in describing the era in golf where Tiger Woods, Vijay Singh, Ernie Els, Retief Goosen and Phil Mickelson dominated the game of golf. The five switched up and down the top five positions in the World Golf Ranking; most notably Vijay Singh's derailment of Tiger Woods as the best golfer in the world. The five stayed, for the most part, in the top five spots from 2004 until the start of 2007. Nine majors were won between them, many fighting against each other head to head.  In July 2005, Els injured his left knee while sailing with his family in the Mediterranean. Despite missing several months of the 2005 season due to the injury, Els won the second event on his return, the Dunhill Championship.
Question: What is the Big Five?. Whats the answer?
the era in golf where Tiger Woods, Vijay Singh, Ernie Els, Retief Goosen and Phil Mickelson dominated the game of golf.