RECENT PHENOMENON. “Men in the US began smoking cigarettes in large numbers in the early 20th century, but it wasn’t until decades later that large numbers of women began smoking regularly. In addition, women who began smoking in the 1950s or later started smoking at an earlier age and smoked more heavily.”
http://www.cancer.org/cancer/news/risk-of-lung-cancer-death-increased-during-last-50-years-for-women-smokers