This paper examines the innovative history of a number of UK firms usi
ng two large databases, looking for evidence consistent with the view
that firms that innovate typically do so persistently. The first sampl
e contains 3304 firms which registered at least one patent in the US a
t 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.