2.8485 x^3 - 3.3892 x^2 - 0.43^x + 1.0373≈-0.0553263 at x≈0.425704 (y=0.459799)
Within cities, and with year fixed effects, the only things that matter are the number of singleton/multitons and the number of hulls. The more singletons/multitons, the greater the growth; and the more hulls, the lower the growth. This result goes away if we control for the full set of geographic characteristics. Without city fixed effects, only avgdisthm is significant (and negative).
===Instrumental Variable(s)===