If Social Policy Bonds were ever to be issued, they would benefit from the work already being done to quantify even such complicated things as human wellbeing - see, for instance, the Human Development Index. Now it appears that people are trying to aggregate and quantify climate change. A group called the International Geosphere-Biosphere programme has launched the 'IGBP Climate-Change Index'. This and the HDI would need refinement before they could be explicitly targeted, and there would always be debate about what they should include and relative weightings.
Even then, they might not be perfect as policy instruments. But what is the alternative? In the absence of explicit targets that are meaningful to ordinary people we are seeing the good intentions of politicians being almost entirely hi-jacked by the short-term financial interests of rich corporations. If that sounds far-fetched, you have only to look at the levels and persistence of government (taxpayer) support for the banks.
We the paying public can't do anything much except admit defeat and settle back for the next set of bills. In the meantime, perhaps we should try and think of a name for the new economic system, which certainly isn't capitalism: that, remember, is all about 'creative destruction', and the freedom to fail. That's exactly what we don't have. The most accurate term would probably be 'bankocracy'. Bankocracy, John Lanchester, 'London Review of Books', 5 November