260 Human Factors of a Global Society
reviews from professional journals. The study yielded the following results concerning markets with
the presence of network effects:
• Market leadership changes frequently and a new leader appears every 3.8 years, on average.
• Change in market leadership is generally associated with a change in quality the same year
or a few years earlier.
• Both network effects and quality determine market share, but quality seems to be more
important.
• Even in the presence of network effects, the market is efcient.
The results described above can be conrmed by the changes that took place in the years 1984–
1997 in the word processor market, an industry being considerably inuenced by network effects.
Word processors ...