Samtskhe-Javakheti Roads 2007-2012

The sample for the first round used the 2002 Census to identify a sampling frame of 732 settlements around either the project or comparison roads, of which 690 were surveyed. The sample size was increased for the second and third rounds, which conducted surveys in all settlements that met at least one of the following criteria: settlements along the SJ Road; settlements along comparison roads where traffic counts are conducted; settlements included in the Integrated Household Survey (IHHS) that the evaluation uses to evaluate household-level outcomes, and any other village that was included in the baseline. The second and third rounds each included 960 settlements.

Our approach to selecting the comparison roads uses the technique of Propensity Score Matching (PSM) to identify eight comparison road segments to be included in the analysis. The comparison roads were selected from an inventory of 117 road segments for which data on a variety of characteristics was available from RDMED, the Georgian government roads agency. Our application of PSM in this case is to estimate a logistic regression model of the probability that a road is part of the treatment group as a function of observable characteristics. We then calculate the predicted probability (or propensity score) that a road segment is part of the treatment group for each of the eight treatment roads and 117 potential comparison roads using these estimated regression coefficients. Finally, each of the eight treatment roads is matched to a single comparison road for which the propensity score is the closest in value from among the 117 potential comparison roads.