In 88 poor countries for which we have data, in each and every one of the 88, the PPP for food shows that poor people can buy less food than you would expect from the PPP that the World Bank is using. The reason for this is obvious on reflection. It has to do with the fact that most foodstuffs are tradable commodities: basic foodstuffs, such as rice, flour and beans, can easily be conveyed across national borders and their prices will therefore roughly mirror the exchange rates among currencies.

A few hundred years ago, perhaps 85 or even 90 percent of humanity lived below a standard of living that today only 40 or 45 percent fail to reach. But at that earlier time only part of this poverty could have been eradicated, and this at substantial cost not only to the pleasures of the affluent, but also to their well-being and to human culture. In our time, nearly all severe poverty could be eradicated at a cost to the affluent that is truly trivial.

It is irrational to charge high prices for socially valuable innovations as this guarantees that they will be underutilized. It is much better to sell them at cost and then to reward the innovator in some other way. This is not always possible, because in some cases the value of an innovation is in the eye of the beholder; it's very difficult to value how much a new Madonna song is worth, for example. But in the case of medicines, green technologies and seeds in agriculture, such an alternative reward mechanism is fairly straightforward.

Feudalism is an economic system where a few people own all the land and the others have no option but to be serfs on such a feudal estate. We now condemn feudalism. We condemn not merely the feudal lords but we condemn the whole structure of rules that sustained feudalism. I am asking people to think similarly about the world economy.

I think one big improvement would be if we somehow made it cheaper and easier for developing countries to learn from the sad experience of some of the developed countries, and also from some of the positive experiences we have of building good transportation systems, like high-speed rail.

By using general consumption PPPs, the World Bank is, in effect, saying to the poor: "Sure, you cannot buy as much food as the dollar value we attribute to your income would buy in the United States. But then you can buy much more by way of services than you could buy with this PPP equivalent in the United States." But what consolation is this? The poor do not buy services - they are services, on their luckier days.

Often vastly more important, international agreements are not routinely published in draft form or publicly debated, and civil society organizations and ordinary citizens often learn of important global institutional design decisions only after they have already been finalized and adopted. The only reliable way to be kept informed and to exert timely influence is by lobbying and paying the politicians and their negotiators.