Sequential Threshold-Spatial-Quantile Panel Estimation // Implements a sequential panel estimation protocol for regional economic panels that combines three estimation layers in a fixed order. The first layer applies a two-way fixed effects baseline. The second layer applies the panel threshold regression method of Hansen (1999) doi:10.1016/S0304-4076(99)00025-1 to identify structural breaks at an unknown threshold of a moderating variable, with bootstrap inference following Hansen (2000) doi:10.1111/1468-0262.00124. The third layer applies a spatial Durbin model with an impact decomposition following LeSage and Pace (2009, ISBN:978-1-4200-6424-7) to quantify direct and indirect spillover effects. The fourth layer applies the two- step panel quantile estimator of Canay (2011) doi:10.1111/j.1368-423X.2011.00349.x to document distributional heterogeneity in the outcome. The threshold identified in the second layer defines a subsample used as structured input to the fourth layer, and a consistency check evaluates whether the three sets of results are jointly compatible with a common underlying structural relationship. An illustrative panel of 33 districts of the state of Maharashtra, India, observed over 10 agricultural years, is included with the package.