Trust is what makes the economy work. Which is a big reason it isn’t working right now.

The more we trust one another, the more willing we are to work together, to buy and sell, to do business. In recent years, academic economists have made a cottage industry out of the question of trust, and in case after case they’ve found that in regions and countries where levels of trust are higher, so is economic growth.

Paola Sapienza at Northwestern’s Kellogg School of Business and Luigi Zingales at Chicago’s Booth School of Business think that the reason why the U.S. and world economy have deteriorated so quickly is that when the financial crisis reached a boiling point this fall, trust levels crumbled. Lenders are wary of borrowers and bankers’ reputation for honesty is right up there with used car dealers.

“While trust is fundamental to all trade and investment, it is particularly important in financial markets, where people depart with their money in exchange for promises,” the economists write. “Promises that aren’t worth the paper they’re written on if there is no trust.”

The two economists are taking a stab at figuring out exactly how deep the breakdown in trust has been with a new financial trust index. Based on interviews, they gauge household’s level of trust in a variety of institutions. They find that trust in the government has fallen over the past three months, trust in banks has fallen more, and trust in the stock market has fallen even more. –Justin Lahart