startSS: Internal Function
Description
It calculates sensible starting values for bivariate probit
models with non-random sample selection. This is based on an adaptation of the Heckman two-step procedure.References
Marra G. and Radice R. (2013), A Penalized Likelihood Estimation Approach to Semiparametric Sample Selection Binary Response Modeling. Electronic Journal of Statistics, 7, 1432-1455.