global gains five times that lower benefit. In present value terms the net benefit of a ‘central’ Doha outcome ranges from $42 trillion to $113 trillion at the higher discount rate and about four times that at the lower discount rate. The costs range from $50 billion to $450 billion in present value terms, but they are mostly private rather than government costs and are dwarfed by the gross benefits. Today’s developing countries reap the majority of those net gains, as their share of the global economy is assumed to grow throughout this century (although at a progressively slower rate after 2015). Their benefit/cost ratios from the trade reform opportunity offered by the Doha round are between 690 and 900 in the higher discount rate case and between 2700 and 3100 in the lower discount rate case. This is clearly an extremely high payoff activity, if only the political will to bring about a successful conclusion to the Doha round can be found.

If for political reasons the Doha round cannot be brought to a successful conclusion, high-income country governments still have the opportunity to boost their intakes of migrant workers from developing countries. In the migration scenarios, the low-cost (‘high net gains’) case refers to one-off costs of just $14,000 per worker and family (shared equally by the migrants and the host government). For the high-cost (‘low net gains’) case, combined costs of three times the low-cost ones are assumed, or $42,000 per worker and family in the year of migration. In present value terms the global net benefit of that increased flow of migrants for 25 years is shown in Table 11 to be $13 trillion at the higher discount rate and $38 trillion at the lower discount rate. Since costs are so small compared with benefits, the benefit/cost ratios for developing country citizens are again very high, ranging between 100 and 840. This too is without doubt a very high payoff, and one that does not even require multilateral agreement – it simply requires greater benevolence on the part of developed country citizens and their national governments.

# **Social and Environmental Benefits and Costs of Reducing Trade and Migration Barriers**

Because trade reform generates large and on-going economic gains while incurring comparatively minor one-off adjustment costs, it would allow individuals and governments the freedom to spend more on other pressing problems, thereby _indirectly_ contributing to the alleviation of other challenges facing society.<sup>30</sup> But in addition, trade reform would also _directly_ alleviate some of those challenges. This section first focuses on the impact of trade reform on poverty alleviation, since that is the solution to many of the world’s problems. It then turns to trade reform’s impact on the environment, before briefly commenting on its impact on several of the other specific challenges being addressed in this project, namely, communicable diseases, conflicts, under-investment in education, corruption, and malnutrition and hunger. The social impacts of migration are briefly canvassed also.

## **_Poverty alleviation_**

Evidence presented by Dollar and Kraay (2002), Sala-i-Martin (2006) and others, and carefully surveyed in Ravallion (2006), suggests aggregate economic growth

> 30 On the intrinsic benefits of freedom of opportunity and action that freer markets provide people, apart from their positive impact in boosting income and wealth, see Sen (1999).

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