Chong et al.

18

**Table 9.** Sexual Activity and Condom Demand: Network Spillover and Reinforcing Interaction Effects

||**Sexually active last**<br>**six months**<br>**(1)**|**Frequency of sex**<br>**last six months**<br>**(2)**|**Number of partners**<br>**last six months**<br>**(3)**|**Redeemed voucher**<br>**for free condoms**<sup>**§**</sup><br>**(4)**|
|---|---|---|---|---|
|Treatment student|0.042|0.340|0.049|0.076|
||(0.036)|(0.313)|(0.039)|(0.058)|
|Spillover student|0.016|0.174|0.032|0.056|
||(0.032)|(0.264)|(0.031)|(0.046)|
|Treatment student * % of friends treated|−0.097**|−0.257|−0.115***|0.043|
||(0.038)|(0.440)|(0.042)|(0.040)|
|Spillover student * % of friends treated|0.110|1.850*|0.186|−0.138*|
||(0.085)|(0.986)|(0.114)|(0.069)|
|Number of friends|−0.005|−0.018|0.008|0.009|
||(0.008)|(0.081)|(0.010)|(0.011)|
|Control for baseline value of dep. var.|No|No|Yes|No|
|Mean of dep. var. control group|0.26|1.58|0.37|0.18|
|_P_-value: treatment * (% of friends)<br>=spillover * (% of friends)|0.0195|0.0662|0.0170|0.0335|
|Observations|4,246|3,843|3,868|3,334|

_Source_ : Authors’ analysis from student surveys. _Note_ : Dependent variables not standardized. All outcome variables are assessed six months after treatment. Standard errors clustered at the school level in parentheses. *** _p <_ 0.01, ** _p <_ 0.05, * _p <_ 0.1. Column 1 includes students attrited for written survey but later tracked over the phone. Table does not control for baseline value of the dependent variable, because outcome was not measured at baseline (except for column 3).<sup>§</sup> 3,358 students of the full sample agreed to be contacted for this part of the study. Specification controls for whether individual had a cellphone.

Overall, while the anlysis reveals that network effects are clearly identified among treated students, it is not surprising that the study had little power to detect network effects among spillover students given the very few friendship network links that occur across classrooms in the data.

# Cost-Effectiveness and Cost-Benefit Analysis

The marginal cost of the Profamilia course is approximately $14.60 per student. The bulk of this cost ($10) is accounted for by the remote tutor, and the remainder comes from Internet platform costs and computer depreciation. The calculations do not include opportunity costs of the time of the students (such as some alternative educational activity, leisure, or work outside of school).<sup>23</sup> Compared to noncomputer-based sexual health interventions in the United States, which range from $69 to more than $10,000 per student,<sup>24</sup> the Profamilia course is extremely low cost. It is also low cost compared to instructor-led programs in developing countries. Kivela, Ketting, and Baltussen (2013) report costs per student of teacher-led school based sexual education programs of $27 in Kenya and $85 in Indonesia.<sup>25</sup> Table 10 presents the cost effectiveness and cost-benefit calculations. These estimates obviously rest on many assumptions, but they provide much value for policy makers by allowing for comparisons across different interventions.

The key result is that students who take the course are 9.9 percentage points more likely to redeem the condom voucher. For the purposes of table 10, the assumption is made that this indicates a consistent condom user. This makes it possible to link the coefficient to the literature documenting the effect of

> 23 The calculations also exclude the wage cost of the person supervising students in the computer lab because it is unlikely that a school would hire personnel exclusively for the course. This is in line with guidelines by Dhaliwal et al. (2013), who argue that cost-effectiveness should use marginal costs of adding the program, assuming fixed costs are incurred with or without the  program.

> 24 Chin et al. (2012), pp. 280, with inflated estimates to 2012  dollars.

25 Costs refer to one semester of the course and are expressed in 2012 U.S. dollars.