This famous econometric study find that, once a state enters ‘fragility’, it is likely to take considerable time to exit that status. The costs of fragility, both to the state itself and its neighbours, are extremely high, estimated at around $80 billion. It stresses the importance of a ‘turnaround’, when a fragile state begins to improve its policies and institutions. It finds that technical assistance delivered before a turnaround has begun has no discernible effect, but can be highly effective after that – that is, it is effective only when a country both wants and needs it.  Other forms of assistance are most effective during the middle of the first decade of reform (5th to 8th year of the turnaround).  More of Collier’s work can be found on his website.