"After the Pill was introduced in the mid-1960s, fornication and 'shacking up' both almost doubled in a period of only five years. This behavior also increased steeply when abortion was legalized in 1973. People of all ages (but especially teenagers) are fornicating more than ever before. Wife-swapping clubs, sex addiction treatment organizations, hard-core pornography, and 'fantasy [sex] tours' to Far East nations have increased tremendously. Even the original developers of the birth control pill now acknowledge that their invention has led to widespread promiscuity. Dr. Robert Kirstner of Harvard Medical School said that "For years I thought the pill would not lead to promiscuity, but I've changed my mind. I think it probably has." And Dr. Min-Chueh Chang, one of the co-developers of the birth control pill, has acknowledged that "[Young people] indulge in too much sexual activity ... I personally feel the pill has rather spoiled young people. It's made them more permissive.""