Ordinary people like you and me can achieve very little on their own. We need to build support. Even if you are a thought leader and have some good ideas on how to make the world better, and even if you write five or ten books - that won't have much effect unless you have people who are willing to support your ideas.

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.

For the present system to work, poor people must be excluded from the innovation, because if they could get access at an affordable price, then affluent people would find ways to buy it cheaply as well - and then the innovator would be poorly rewarded and introductions of new medicines would decline.

Think of US slavery in 1850, or the subjection of women. Both of these injustices could have been - and were! - defended by pointing out, quite correctly, that this situation of slaves and women had been improving throughout the preceding century. Slaves, in particular, were worked less hard, beaten and raped less frequently, better fed, and less often ripped apart from their families. So would a celebration of moral progress have been appropriate in 1850? Surely not. Slavery could have been and should have been abolished - then, if not before.

America is run by the rich and powerful in their own interest. To an extent that I think is hard to exaggerate, the intellectuals - academics, journalists and so on - are bought off. And that's a big change that happened in the United States in the last 30 or 40 years.

Purchasing power parities are not a reasonable method for comparing households across countries or currencies. The reason for this is simply that PPPs are sensitive to the prices of all the commodities, goods and services, that households are consuming worldwide, with each commodity weighted in the calculations according to its share in international household consumption expenditure.

Dictatorial regimes often manage to keep themselves in power because they are recognized by foreigners as representing the state and its people, and therefore as entitled to sell the country's natural resources and to borrow money in its people's name. These privileges conferred by foreigners keep autocrats in power despite the fact that they were not elected and do not rule in the interest of the population.