The average age of a participant in a typical study is 35 to 45 years old, with only two studies focused on young entrepreneurs (Bruhn and Zia, 2012; Premand et al, 2012). Some studies focus entirely on female business owners, others on entirely male owners, while relatively few have sufficient numbers of both genders to compare impacts separately. Finally, there is substantial heterogeneity in the education levels of the participantswith averages as low as 2.5 years of schooling for females and 5.7 years for males in the rural Pakistan study of Giné and Mansuri (2011) and as high as university level in the course of Premand et al. (2012).

Table 2 shows the degree of heterogeneity in firm size at baseline among studies that include existing firms. At the low end are the subsistence firms run by women in Giné and Mansuri (2011) and de Mel et al. (2012), where 95 percent of the firms have no paid employees, and average monthly revenues are only US$80-100 at market exchange rates, and profits are approximately one dollar per day. Most of the rest of the studies also focus on microenterprises, albeit ones with slightly larger revenues and potentially one or two employees. The main exceptions are the firms chosen from industrial clusters (Mano et al, 2011 and Sonobe et al, 2012), where the firms are SMEs with 5 to 50 workers, and monthly revenues which are $5000 or more (and in some cases over $100,000).

# _Training Delivery and Costs_

All of the training courses reviewed here are classroom-based and delivered to groups of individuals, although several of the programs provide additional one-on-one follow-up training, which we will discuss later (as well as discussing three individualized consulting experiments separately). Table 3 provides key characteristics of the training delivery in the different studies. A first point to note is that many of the studies are testing content that has been modified or developed specifically for the study of interest, rather than content that has been taught for years. This may matter if it takes time to adapt particular content to local context or for instructors to become familiar with the material. The instructors in most studies are experienced training professionals, although in a few studies microfinance officers themselves have been trained to deliver content. Berge et al. (2012) compare the same training content taught by microfinance staff and by professional trainers, and find that in the courses taught by microfinance staff, attendance rates fall more and both subjective evaluations of course quality and understanding of the concept of profits in tests are lower. As a consequence of differences in the newness of the content and in who provides it, the quality of training is likely to vary across studies.

The length of the training course also varies substantially across studies. The shortest courses are two days or two half-days (Bruhn and Zia, 2012; Field et al, 2010), while other courses are for one week or more full-time (e.g. de Mel et al, 2012; Sonobe et al, 2011). In most cases the training is concentrated over a relatively short period of time, but in some of the cases where training takes place in microfinance group meetings, it can be spread over many months, with as little as half an hour per month over many months (e.g. Karlan and Valdivia, 2011). Longer full-time courses allow more content to be taught, but are more costly, and also require business owners to be away for their businesses for more time.

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