
by year of application, and weight these by future citations through
2002 (see Aghion et al. (2013)).
</p>
<p>The presample average of cite-weighted patents (precites) is used by Aghion et
al. (2013) as a proxy for unobserved heterogeneity, employing the
&quot;presample mean scaling&quot; method of Blundell et al. (1999).
</p>
<p>The inverse Lerner index in the firm's three-digit industry is used
as a time-varying measure for product market competition (competition), where the Lerner is
calculated as the m