Final answer:
The total percentage of GDP associated with manufacturing has decreased since the 1940s due to factors such as globalization and the shift towards a service-based economy.
Step-by-step explanation:
The total percentage of GDP associated with manufacturing has decreased since the 1940s. In 1950, the United States produced 40 percent of goods and services worldwide, but by the 1970s, this percentage had declined to 25 percent. The decline in manufacturing can be attributed to factors such as globalization and the shift towards a service-based economy.