Health R&D unquestionably has GPG aspects, and there is not enough of it in fields that would benefit poor countries. Historically, the public and the not-for profit sectors have carried out research resulting in new drugs and treatments, but the private for-profit sector now plays the largest role [12, 13] . An important policy question is therefore how to encourage private sector firms to engage in research benefiting poor countries and peoples: the ubiquitous '90-10 problem' (that 90% of global R&D spending in health is targeted at diseases affecting only 10% of the world's population) [14] . A related but distinct question is how to bolster the demand for drugs in low-income countries (and hence firms' willingness to engage in R&D); we touch on this in a section below in which we discuss Advance Purchase Commitments and other financial innovations.