<human>: Eldrick Tont Woods (born December 30, 1975) better known as Tiger Woods, is an American professional golfer who is among the most successful golfers of all time. He has been one of the highest-paid athletes in the world for several years. Following an outstanding junior, college, and amateur career, Woods was 20 years old when he turned professional at the end of summer in 1996. By the end of April 1997, he had won three PGA Tour events in addition to his first major, the 1997 Masters.

Early in Woods' career, a small number of golf experts expressed concern about his impact on the competitiveness of the game and the public appeal of professional golf. Sportswriter Bill Lyon of Knight Ridder asked in a column, "Isn't Tiger Woods actually bad for golf?" (though Lyon ultimately concluded that he was not). At first, some pundits feared that Woods would drive the spirit of competition out of the game of golf by making existing courses obsolete and relegating opponents to simply competing for second place each week.  A related effect was measured by University of California economist Jennifer Brown, who found that other golfers scored higher when competing against Woods than when he was not in the tournament. The scores of highly skilled (exempt) golfers are nearly one stroke higher when playing against Woods. This effect was larger when he was on winning streaks and disappeared during his well-publicized slump in 2003-04. Brown explains the results by noting that competitors of similar skill can hope to win by increasing their level of effort, but that, when facing a "superstar" competitor, extra exertion does not significantly raise one's level of winning while increasing risk of injury or exhaustion, leading to reduced effort.  Many courses in the PGA Tour rotation (including major championship sites like Augusta National) have added yardage to their tees in an effort to reduce the advantage of long hitters like Woods, a strategy that became known as "Tiger-Proofing". Woods said he welcomed the change, in that adding yardage to courses did not affect his ability to win. CANNOTANSWER

Answer the following question by taking a quote from the article: What does tiger-proofing refer to?
<bot>: Many courses in the PGA Tour rotation (including major championship sites like Augusta National) have added yardage to their tees