Professor Mark J. Perry's Blog for Economics and Finance

What do the companies in these three groups have in common?Group A. American Motors, Studebaker, Eastman Kodak, Maytag and National Sugar Refining.Group B. Boeing, Campbell Soup, Deere, IBM and Whirlpool.Group C. Cisco, eBay, McDonald's, Microsoft and Yahoo.All the companies in Group A were in the Fortune 500 in 1959, but not in 2009.All the companies in Group B were in the Fortune 500 in both 1959 and 2009.All the companies in Group C were in the Fortune 500 in 2009, but not 1959.Here's the complete database of the Fortune 500 every year from 1959-2009. Comparing the Fortune 500 in 1959 to 2009, I find that there are only 72 companies that appear in both lists. In other words, only 14% of the...