6. **Contrasting experiences – comparing project impacts for the younger and older cohorts** As described at the outset, the impact evaluation of the Indonesia ECED Project followed two cohorts of children. The focus of the paper so far has been on the younger cohort. The impacts of the intervention on the older cohort have previously been published (Brinkman et al. 2017b).

As shown in Figure 1, the data collection schedule meant that both cohorts of children were surveyed when they were age 5 and age 8. In this section, we contrast the impact estimates of these two cohorts side-by-side.<sup>16</sup> Table 5 presents the impact estimates at age 5 and age 8 for each cohort. Columns 1 and 4 are the results for the younger cohort previously shown in Tables 2 to 4 in this paper. Columns 2 and 5 present the equivalent results for the older cohort, previously reported in Brinkman et al., 2017b. Column 6 presents test score results for the older cohort, which have not previously been published.<sup>17</sup> Columns 3 and 7 show the results of a _t_ -test comparing the differences in impact between the two cohorts.<sup>18</sup> Overall, we find that the project impacts differed between the older and younger cohorts. The results are consistent with the fact that the _experiences_ of the older and younger cohorts were different along two key dimensions: (1) the phase of implementation when they were exposed to project playgroups and (2) the length of exposure to project playgroups at the appropriate age (3-4 years old). On the first dimension, children in the older cohort were exposed to the project in its first year whereas children in the younger cohort were exposed to a more mature project in its third year of implementation. On the second dimension, children in the older cohort were capped (at most) to one year of age-appropriate enrollment in project playgroups because they were already age 4 when the project began. In contrast, children in the younger cohort were only age 1 when the project began so they were more likely to enroll in project playgroups at the appropriate-ages of 3 to 4.

Table 5 shows that the younger and older cohorts had very different rates of enrollment in various types of early childhood education. Children from the younger cohort in treatment villages were 49.9 percentage points more likely to enroll in project playgroups compared to children from comparison villages. In contrast, the estimate for the older cohort was only 15.3 percentage points. This corresponds to a difference of 34.6 percentage points when the two cohorts were age 5. By age 8, the difference in impacts between the two cohorts had declined somewhat but was still very large. The effect on project playgroup enrollment for children in the younger cohort was 22.9 percentage points higher than that for the children in the older cohort.

For enrollment in non-project playgroups, the impact was a 22 percentage point decline for the younger cohort compared to 4.4 percentage point decline for the older cohort. By age 5, children in the younger cohort were 17.6 percentage points less likely to be enrolled in non-project playgroups compared to the older cohort. These differences in estimates were fairly similar by age 8, with a 15.2 percentage point difference between the two cohorts.

For kindergarten enrollment, the point estimates for the two cohorts were not

> 16 See Appendix B for the empirical strategy used to estimate the impacts for the 4 year-old cohort. 17 These are obtained using the approach described in Appendix B. The items used to construct scores for the 4 year-old cohort are identical to those used for the 1 year-old cohort.

> 18 Our test statistic to examine whether the estimates from the two cohorts are statistically different is � � � ����������������� �������� � ����������������� ������������������� ��� � ,���� � ���� � �������������������������� ����� � assuming 2Cov�β� , β��� � ��0��� . Since Cov�β� , β��� � ���� is typically positive, our assumption yields a conservative estimate of the test statistic.

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