connyc 's Profile

Of course, this industry has undergone large changes
since 1990, including consolidation among many of the largest pharmaceutical
companies and significant growth in the number of biotechnology
companies. But, by examining the period before the growth of the
internet, we can gain some key insights. A potential benefit of
the internet and other advances in information technology is that
knowledge may now be shared almost instantaneously and at very
low cost. To assess the relevance of this potential benefit, it
is important to understand whether knowledge spillovers have historically
been localized, or limited by geography.

This problem has been dealt with in the caseload literature by estimating models that include state-fixed effects and state-specific trends. State-fixed effects control for unobservable determinants of welfare use that vary between states but remain constant within states over time. State-specific trends further control for unobservables that trend linearly within states over the sample period. Policy endogeneity persists, however, if welfare reform in a state is motivated by unobservable determinants of welfare use that are neither fixed nor smoothly trending.

State-year-fixed effects provide controls for all state-level unobservables regardless of how they might vary over the sample period

vast majority of Amazon MP3 customers, who are fine with
the idea of buying digital music (since they're shopping at Amazon MP3), had previously refused to buy their music from Apple.

one company will not dictate the
terms of digital music distribution