"between 1980 and 2014, income inequality in the united states has increased in part due to expanding international trade. how does expanding international trade"?

See explanation below.

Explanation:

On this case we can conclude that the USA firms with this condition now can hire people with not qualifications anywhere in the planet, on this case this situation allos that the people from USA would be in competition with foreign workers.

And as a consequence we have that the wages sometimes are not equitative in som situations. And that's a competitiv situation on which the people from USA sometimes needs to accept lower wages in order to get a job in the country.  

for many centuries there were important factors which the economies of the muslim empires developed increasingly. they applied economic procedures in production, investment, finance, taxation and property. they used to tax certain goods (for example: harvest), they charged interest on money lent, they signed contracts with merchants; they relied on a common currency, and they used checks as well as promissory notes. with the money collected by means of taxation, the government provided the needy with an income. in addition, trading networks covered huge distances, so far regions started to have contact and exchange goods. this trade network covered areas of asia, africa and europe.