Migration is a new area of research for me.  From my point of view the interesting question is "can one construct politically viable mechanisms to create more 'development friendly' movements of people across national borders?"  

The Future of Migration:  Accommodating Irresistible Forces and Immovable Ideas.  This is a manuscript, in preparation for publication by the Center for Global Development, that argues that the "development community" should be much more active in putting labor mobility on the international agenda along side trade, aid and debt. 

Policy 'think piece'.   This is a short "think piece" prepared for the Center for Global Development on industrial country policies towards the mobility of unskilled labor. 

The Future of Migration:  Irresistible Forces Meet Immovable Ideas.  (October 2003).  This paper, presented as a talk at a recent conference at Yale on globalization, examines the forces in the world pushing for greater flows of people across borders, and the ideas, particularly in the rich industrialized world that are blocking those flows.  Also attached is the presentation at the conference.

Boomtowns and Ghost Countries:  Geography, Agglomeration and Population Mobility (November 2003).  This paper suggests that the combination of negative geographic shocks and forces of agglomeration could lead to 'ghost countries' in the world.  By analogy with "ghost towns" these are countries in which the current desired population is a small faction of its previous peak (or current).  

This picture shows the growth of population of regions (states, provinces) within Canada, USA, and Japan and the growth of GDP per capita in those same regions as 90th/10th percentile rectangles (unadjusted for any correlation).  Also shown is the 90/10 ratio for non-OECD countries.  Not surprisingly, when populations are mobile these are long rectangles as difference in population growth are larger than differences in GDP per capita.  In contrast, when labor is largely immobile then the rectangle is tall and thin--countries differ much more in GDP per capita growth than in mobility (population growth less rate of natural increase). 

This is of course consistent with large, persistent regional specific shocks to labor demand--when labor supply is elastic this leads to large population changes, when labor is inelastic this leads to large changes in wages.

The paper also shows the decline in population in regions of the USA, county by county.  The simple point is that there are large, geographically contiguous regions of the USA that have seen absolute declines in population over the 1930 to 1990 period.  If there have been large decline sin the "desired"  population of regions of the USA--then why not of regions of the world that are nation-states? 

I have presented some combination of these papers a number of times--at NYU, at Harvard's Center for Population Studies, and at the KSGs MPA/ID program (all with different emphasis).