Because so many of the 100-year-old local companies I had interviewed were small (less than 100 employees), I had surmised that many old companies tend to remain small - a result, perhaps, of an emphasis on survival rather than growth. However, once we assembled our data base of U.S. companies over 100 years old, we discovered that only about one-third of the companies would be considered "small" (under 100 employees). We know that we are missing many small local companies that simply haven't come to our attention and are not in any of the state records we have been able to find, but this still is a far smaller percentage than for U.S. companies overall (where over 95% of the companies have under 100 employees).
However, over 50% of the companies in our data base are "large" - over 500 employees - compared with only 1% (or less) of U.S. companies overall. The only size category where old companies and all U.S. companies appear to be similar is that of medium-sized businesses - those with 100-500 employees.