Real disposable income is the real amount of purchasing power that people have after they pay taxes to the government. This is the money that people have available to purchase things (consumption) or to set aside for future investment (saving).
For people in other countries to be able to buy U.S. goods, they need to have enough real disposable income to do so. This is why high income countries like Canada or Japan import more things from the U.S. than low income countries like El Salvador or Nigeria.
