Maybe a lot.
"In the early 1970s, the percentage of married women keeping their own name was less than 5 percent. But the trend took off later that decade, with more than 20 percent of women keeping their (mostly) maiden names in the late 1970s and 1980s, according to analysis by Harvard University economics professor Claudia Goldin. Then, what was old became new again. ...23 percent of college-educated women kept their name in 1990, but only 17 percent did in 2000."
The article leads off with the story of an Atlanta news anchor who changed her last name to that of her fourth husband's. "'For me it was a personal statement about my commitment to my marriage,' Pearson said. 'People say Monica Kaufman is your brand, but I am a human being first.'"