In the 1950s, imports and exports of goods and services constituted roughly 4% to 5% of U.S. GDP. In recent years, exports have accounted for approximately 12% of GDP, while imports have more than tripled to over 15% of GDP. Which of the following help explain the increase in international trade and finance since the 1950s? Select all that apply
a. International trade agreements such as the General Agreement on Tariffs and Trade (GATT)
b. Higher tariffs
c. Better high-speed rail lines
d. Services such as web conferencing and teleconferencing that facilitate international meetings