Main varieble	Definition
log(income_ijdt)	$I n c o m e G r o w t h_{i j d} = \ln (i n c o m e_{i j d, T}) - \ln (i n c o m e_{i j d, t})$
age_ijdt	2006 minus the firm’s start operation year
VD_ijdt	$V e r t i c a l D i s i n t e g r a t i o n_{i j d t} = \frac{p u r c h a s e d i n t e r m e d i a t e i n p u t_{i j d t}}{g r o s s o u t p u t v a l u e_{i j d t}}$
log(popdes_ct)	the 2006 population in city c per square-kilometer
RV_dt	$R V_{d t} = \sum_{j = 1}^{J} P_{j d t} \times [\sum_{g \in j} \frac{p_{g d t}}{P_{j d t}} \log_{2} (\frac{1}{p_{g d t} / P_{j d t}})]$
UV_dt	$U V_{d t} = \sum_{j = 1}^{J} P_{j d t} \log_{2} (\frac{1}{P_{j d t}})$