How persistently do firms innovate?

This paper examines the innovative history of a number of UK firms using two large databases, looking for evidence consistent with the view that firms that innovate typically do so persistently. The first sample contains 3304 firms which registered at least one patent in the US at any time in the period 1969-1988, while the second consists of 1624 firms which produced at least one major innovation at any time in the UK from 1945 to 1982. Both data sets yield the same conclusion, namely that very few innovative firms are persistently innovative. (C) 1997 Elsevier Science B.V. All rights reserved.