The NY Times provides some insights:

According to the Bureau of Labor Statistics, the overall median age of American workers is 42.3 years old. The company with the oldest workers on the PayScale list, Hewlett – Packard, came in at 41 years… I.B.M. Global Services (38 years old), Oracle (38) …

The … companies with the youngest workers, ranked from youngest to highest in median age, were Epic Games (26); Facebook (28); Zynga (28); Google (29)…

Source: Technology Workers Are Young (Really Young) By QUENTIN HARDY. NY Times