Why are rich countries democratic?

Ricardo Hausman, a Professor at Harvard University, writes on the necessity of proper democracy (beyond voting cast) through decentralizing the power and empowering the legislation to monitor government activities. The main theme of the article comes in the following way:

"... successful political systems have had to create an alternative invisible hand – a system that decentralizes the power to identify problems, propose solutions, and monitor performance, such that decisions are made with much more information."

Link for the article.