Neoclassical attempts to explain long-term economic growth have met wi
th very limited success. Strong empirical confirmation is lacking and
the theoretical foundations of the approach are insecure. The present
article sketches an alternative ''evolutionary'' theory of long-term g
rowth and extends preceding work by the author in the area. Major stre
ss is placed on institutional disruptions such as wars or revolutions
and on the existence of political institutions such as multi-party dem
ocracy. Inspiration is taken from both the earlier ideas of Thorstein
Veblen and the recent work of Nelson and Winter. A microeconomic proce
ss explaining the effect of disruption on productivity growth is also
outlined. An econometric test confirms some of the major propositions
in the article.