4 pro-social preferences and explicitly measure preferences for serving the disenfranchised group (the poor).

Prior experiments distinguish the health status of patients but not variations in the “difficulty” (i.e. level of effort required) of dealing with patients, holding heath status constant. In contrast to the tasks used in earlier experiments, our video vignettes allow us to better simulate the complexity of patient visits and to identify separately the effort required to serve poor and non-poor patients.

The analysis contributes to the large behavioral literature on intrinsic and extrinsic motivations. One theme in that literature is the interaction of pro-social and extrinsic motivations on effort: piece rate or salary-based compensation, for example, or task versus mission motivation (Frey and Oberholzer-Gee 1997; Deci and Ryan 1999, Delfgaauw and Dur 2008). Dal Bó, Finan and Rossi (2013) and Banuri and Keefer (2016) examine how pay levels affect selection into public sector positions of more capable and mission-motivated workers. Jones, Tonin and Vlassopoulos (2018) extend this work to show intrinsic and extrinsic motivation affect effort across multiple tasks. Ashraf et al., (2014) find that agents who are offered non-financial rewards exert more effort than those offered financial margins or volunteer contracts. Banuri, Keefer and de Walque (2017) examine the interaction of two intrinsic motivations, pro-sociality and task enjoyment, and find that the first has no additional effect on effort when the second is high. Ours is the first study that identifies a significant effect of pro-poor preferences, distinct from pro-social preferences, and demonstrates a large and significant interaction between pro-poor preferences and extrinsic incentives.

# **3. Motivation**

The positive relationship between life expectancy and per capita income is well known (see Figure 1 for this correlation across all countries in 2014). Figure 2 focuses on Burkina Faso. In 2010, child mortality in Burkina Faso was 97 per thousand live births in the richest wealth quintile but 175 among the poorest quintile; similarly, 93.2 percent of women coming from the richest quintile delivered in a health facility, but only 46.1 percent of those in the poorest quintile did so (Institut National de la Statistique et de la Démographie - INSD/Burkina Faso and ICF International, 2012). In the past decade, Burkina Faso has introduced several reforms that aim at improving financial access to health services for the poor, including the reduction of user fees for obstetric services in 2007, exemption of user fees for the worst off (les indigents) in 2009, ResultsBased Financing, which introduced pro-poor incentives to health care providers in 2014, and generalized free health care for women and children in 2015 ( _la gratuité_ ).<sup>3</sup> Globally, this (considerable) effort to improve health outcomes among the poor has had mixed impact.

Moreover, researchers have noted that simply expanding resources for health care may widen these disparities. Gwatkin (2005) warns that because expanded health services typically reach wealthier groups before disadvantaged ones, poor people are unlikely to be the main beneficiaries of efforts to accelerate progress towards the health Millennium Development Goals (MDG) by providing additional resources to the health sector. Analyzing nationally representative surveys in 64 developing countries over the 1990-2011 period, Wagstaff, Bredenkamp and Buisman (2014), establish that the poorest 40 percent have made faster progress than the richest 60 percent on MDG

> 3 A recent study on the reduction and exemption of user fees showed that the majority of public sector health workers were unaware or at least did not understand these directives, and this contributed to weak implementation and adherence to the policy changes (Ridde et al., 2018).