  Evidence is growing that in many markets consumers select not simply on the
basis of the perceived attributes of products, but their preferences are
modified by the behaviour of others. Economists have paid relatively little
attention to such markets. The classic Bass diffusion model incorporates the
imitation of others as a part of the behavioural rules used by consumers in
making choice. We extend the Bass model to be able to apply it to long-term
case studies where substantial changes over time in the population making
choices at any given point have to be taken into account. We consider evidence
from the activity of hill-walking. We use as a particular illustration the
Munros, a list of Scottish hills over 3,000 feet in height which many British
walkers aspire to complete. The extension to the Bass model can of course be
used in other situations where such population changes are important.
