who do not receive contributory pensions, we compared them to the average change of an alternative control group, that is, we compared the treatment group to the average change on the group of adults 56 to 59 years old.

The estimated effects of the expansion of PAM on the extreme poverty headcount index using the alternative control group are slightly smaller than with the original control group with an estimated reduction in the probability of being extreme poor of 3.4 percentage points compared to a 5.4 with the original control group. The results, however, are consistent, of similar magnitude, and statistically significant at the 5% level. These results are shown in Table F.9 in Appendix F.

The estimated effects on the extreme poverty gap index and on the extreme poverty severity index are somewhat larger when using the alternative control group, but still in the same direction and statistically significant at the 1% level (Table F.10). The results obtained of the effects of the program’s expansion on multi-dimensional extreme poverty using the alternative control group are similar to the ones obtained when using the original control group. The estimation using the alternative control group showed a reduction of 4.4 percentage points on the probability of being extreme poor according to the multidimensional extreme poverty index, while the results obtained with the primary control group showed a reduction of 5.8 percentage points. Table F.11 in Appendix F shows these results.

In addition, when we ran the same model without excluding, from the treatment and control groups, those adults who receive contributory pensions, the estimated effects remained consistent with those obtained when contributory pensioners were excluded. Similarly, we ran the same models without excluding Chiapas and Mexico City data; instead, we used dummy variables to indicate whether an observation was from either one of these states. The results obtained using this approach were consistent with our main results.

# **3.6.3 Treatment-on-the-Treated Effects (TOT)**

Table 10 shows the first-stage result of the estimation of the TOT effects using 2SLS. These results confirm that the instrument is effectively correlated with the variable it is instrumenting for, that is, the interaction term _treat*year2014_ is correlated with the binary variable that indicates program participation, _p_pam_ , and is statistically significant at the one 1% level.

The second-stage results of the 2SLS suggest that the expansion of PAM reduced extreme poverty. The results show poverty reducing effects on the treated population between 6.1 and 13.2 percentage points, depending on the poverty measure considered. Table 11 shows that the program had reducing effects of 11.5 percentage points on the probability of being extreme poor as measured by the headcount index, 7.9 percentage points on the poverty gap index, 6.1 percentage points on the poverty severity index, and 13.2 percentage points on the probability of being extreme poor as measured by the multidimensional poverty headcount index. These results are statistically significant Previously, we explained our assumption that _p_ pam_ is endogenously correlated with the error term of the simple linear regression of _p_ pam_ on extreme poverty or labor supply variables. This could 25