iop - Inflated Ordered Probit and Logit Models
Estimation, inference, and quantities of interest for
ordered probit and ordered logit models whose outcome contains
an inflated category: a single ordered category (bottom,
middle, top, or any other) that mixes observations generated by
the ordered process with observations generated by a distinct
split-population process. Fits the zero-inflated ordered probit
of Harris and Zhao (2007) <doi:10.1016/j.jeconom.2007.01.002>
and its middle- and top-inflated extensions (Bagozzi and
Mukherjee 2012 <doi:10.1093/pan/mps020>; Bagozzi, Hill, Moore
and Mukherjee 2015 <doi:10.1177/0022002713520530>; Bagozzi, Joo
and Mukherjee 2024 <doi:10.1093/fpa/orae006>), generalized to
an arbitrary inflated category and to the logit link, with
optional correlated errors for the probit form, plus the
standard ordered probit and logit and their partial
proportional-odds (non-parallel) variants on the same footing.
Provides analytic, robust, and cluster-robust standard errors,
survey weights and offsets, model comparison (Vuong,
likelihood-ratio, information criteria), regime-specific
predicted probabilities and first differences, simulation for
residual diagnostics, and tidy/table-package integration. The
likelihood, its gradient, and the bivariate-normal
probabilities are implemented in C++.