Three key features shape these chapters and the resulting rankings sufficiently to warrant some general observations for nonspecialist readers. The first is the curse of diminishing returns.

even minimum data collection would cost at least $254bn,

It is very difficult to know what exactly is promised, how governments should interpret it, let alone how it will be monitored or evaluated.

when resources to improve the lives of the poor are scarce, how can we get these resources to go further – much further?

everywhere in the world and, second, that these costs can be reasonably estimated using one or two well-designed impact assessments from particular times and places.

or almost twice the entire global annual development budget.

properly monitoring all the targets of the Millennium Development Goals would have cost around $27bn.

We can’t do it all. The cost of meeting all of the Sustainable Development Goals would be between USD$3.3 and $4.5 trillion annually according to the OECD,

the Millennium Development Goals. These covered the eight key areas of poverty, education, gender equality, child mortality, maternal health, disease, the environment, and global partnership.