It's well known that the rich have an outsized influence on the economy.

The nation's top 1% of households own more than half the nation's stocks, according to the Federal Reserve. They also control more than $16 trillion in wealth -- more than the bottom 90%.

Yet a new body of research from Citigroup suggests that the rich have other, more-surprising impacts on the economy.

Ajay Kapur, global strategist at Citigroup, and his research team came up with the term "Plutonomy" in 2005 to describe a country that is defined by massive income and wealth inequality. According to their definition, the U.S. is a Plutonomy, along with the U.K., Canada and Australia.

In a series of research notes over the past year, Kapur and his team explained that Plutonomies have three basic characteristics.