of recent major champions, professionals currently ranked high in the world rankings or on the previous year's money lists around the world, and leading amateurs from recent USGA events – about half of the 156-person field still enters the tournament through two rounds of open qualification events, mostly held in the U.S. but also in Europe and Japan. The U.S. Open has no barrier to entry for either women or junior players, as long as they are a professional or meet amateur handicap requirements. As of 2022, however, no female golfer has yet qualified for the U.S. Open, although in 2006 Michelle Wie made it to the second qualifying stage. While the U.S. Open employed an 18-hole playoff for many years if players were tied after four rounds, the USGA announced that beginning in 2018 all of its future championships would implement a two-hole aggregate playoff format. A sudden-death playoff would follow if the players were still tied after the two playoff holes. (This change also brought the U.S. Open more in line with both the Open and PGA Championships, which use four- and three-hole aggregate playoffs respectively, followed by sudden death if necessary, and most regular events as well as the Masters only have simple sudden-death playoffs.) The Sunday of the Championship has also in recent years fallen on Father's Day (at least as recognized in the US and the UK) which has lent added poignancy to winners' speeches. The year's final major, The Open Championship (sometimes referred to as the British Open), is organized by The R&A, an offshoot of The Royal and Ancient Golf Club of St Andrews, and is typically played on a links-style course in the United Kingdom (primarily Scotland or England). It carries the prestige of being the oldest professional golf tournament currently in existence and the original "Open" championship (although the very first event was held only for British professionals). It is respected for maintaining the tradition of links play that dates back to the very invention of the game in Scotland. Links courses are generally typified as coastal, flat and often very windswept, with the fairways cut through dune grass and gorse bushes that make up the "rough", and have deep bunkers. The course is generally not "doctored" to make it more difficult, effectively making the variable weather the main external influence on the field's score. In fact, the greens at Open