The University of Washington has about 30,000 undergraduates, about 500 of which were enrolled in introductory classes in the statistics department. Assuming that number holds every quarter, 1500/30000 = 1.6% of UW students take an intro statistics class each year.
There are 18 million college students in the United States. If the overall percentage who take statistics is the same as at UW, then about 300,000 college students take intro stats each year in this country.