At its inauguration in 1873, the Preakness carried a value of $1,000. The first major increase occurred in 1919 when the race had a $25,000 value. It climbed to $100,000 in 1946 and in 1959 was raised to $150,000. Subsequent increases occurred from 1979 to 1989, when the purse rose four times from $200,000 to $500,000, before going to $1 million in 1997. On December 12, 2013, the Maryland Jockey Club announced for the 2014 running of the Preakness the purse would be increased from $1,000,000 to $1,500,000.
Over how many years did the value of the Preakness raise 4 times from $200,000 to $500,000?
10