In addition to collecting taxes, governments borrow money to spend on investments that will boost their own economies, as well as to meet their spending obligations. In an environment of low-interest rates, it's cheap for them to do so. For a lot of developed countries, this is usually in the realm of millions or trillions of dollars, numbers that we might struggle to comprehend. For example, the gross national debt of Japan is $ 1,000 bn. The gross national debt of the United States is $1,899 bn. Here is a look at per capita debt of different countries: