According to the American Council of Trustees and Alumni, a non-profit that seeks to stir up higher education, there are seven subjects "essential to a liberal arts education: literature, composition, economics, math, intermediate level foreign language, science, and American government/history." Thus, they decided to look at the graduation requirements of about 1100 U.S. colleges and universities, and see if or how the requirements matched their seven categories.
You can see school-by-school data here. Out of the 1100 schools, only 23 had requirements that covered all seven areas. Here's the overall count of how many schools required each of these subjects:
Of course, these kinds of counts are always dependent on the categories chosen, and the categories can be argued. My guess is that a number of schools might have, for example, a "social science" requirement rather than an "economics," or perhaps an overall history requirement rather than a "U.S history/government" requirement. Personally, I'm not the biggest fan of the old-time requirement for learning a foreign language, although that's an argument for another day. As I mentioned, ACTA likes to stir the pot.
That said, a list of requirements tells you something about what common experiences and subjects you can reasonably expect every college graduate to know something about. It tells you something about the willingness of colleges and universities to nudge students just a bit out of their comfort zone. So it's bothersome to me that at about 80% of U.S. colleges and universities, students who wish to do so can avoid taking any economics, or any U.S. history and government.