lamps, respectively.<sup>22</sup> We also use an indicator of whether households currently own a lamp of superior quality. Here, quality is approximated by the price of the most recently acquired solar lighting product which, according to formative qualitative field research, is a good indicator for the quality of the adopted technology.<sup>23</sup> Solar energy knowledge is considered a secondary outcome of interest. Specifically, we use dummy variables for awareness and understanding of pico-PV technology. A household is deemed aware if it reports to use solar lighting products as their primary or secondary lighting source (in response to an unprompted question). A household is also considered aware if it correctly selects ‘sun’ among four possible choices (`dry cell battery’, `wind’, `sun’, `mud’) when asked which sources of energy are able to power a lantern or torch.<sup>24</sup> For solar technology understanding, a household is assigned the value one if it reports that a sunny weather is the best condition for the generation of solar power and zero otherwise.<sup>25</sup> Additional secondary outcome variables consist of measures for quality expectations and locus of control. For the former, participants were asked whether they have heard of the Lighting Global Quality Standards (developed by Lighting Africa) and their expectations regarding the lifetime of a typical solar lamp, which was used to construct a binary indicator for whether expected durability exceeds six months (quality expectation). For comparison, a standard battery-driven torch has a maximum warranty period of two months in rural Senegal. Also, people may not be familiar with other quality features such as brightness measured in lumens. For the locus of control measure, participants were asked whether they feel that what happens to them is their own doing (binary indicator takes the value 1) or that they mostly lack control over the direction their life is taking (it 22 We constructed these outcome indicators based on data from the face-to-face and mobile phone surveys. At baseline, we observe this information only for households that demonstrate basic awareness that the sun is an energy source that can power a lantern or torch (see the definition of the variable related to pico-PV knowledge for more details). Following the survey protocol, we infer that those who do not demonstrate basic awareness have never owned a solar lighting product and adjust all other solar lamp adoption variables accordingly. 23 A price below CAF 1,000 indicates that the solar lighting product is a torch. These are not considered solar lamps in our study. A price above CAF 5,000 commonly indicates that the solar lighting product can emit lumen in all directions and is better able to light up an entire room.

> 24 A change was made to the face-to-face baseline questionnaire that affects this variable. A fifth choice option (`fire’) was removed four days into survey implementation. To eliminate any potential bias from this change, all values recorded prior to this date were set to zero. Also, the response set differs slightly between the baseline and end line surveys. Instead of `battery’, the option `all of the above’ was used in the second mobile phone survey.

25 At baseline, we have this information only for households that demonstrate basic awareness of solar energy. We have additional baseline information in relation to understanding of pico-PV technology. Households were asked whether they would place the solar lighting product inside the house, outside the house, or outside the house in the sun to maximize lighting hours.

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