For much of the 20th century, humanity had been blessed with spare capacity — the ability to produce good, services, and commodities in quantities greater than required to sustain the current population and its desires.
Much of this can be attributed to technological improvements. For instance, medical advancements, particularly in antibiotics, automation in agriculture, and readily available energy from hydrocarbons, enabled longer lifespans, for more people, with ample food, requiring relatively little labor.
Some of this can also be attributed to efficiency improvements. A greater portion of people living in cities meant more efficient distribution and network dynamics. Similarly, improvements in transportation, communication, and cheap energy, enabled global networking — globalization of trade. The latter in particular unlocked imbalances, such as cheap labor in one country providing the importing country with cheap capacity.
Growth of many of these forces is slowing, or even reversing. The lowest hanging fruit from globalization have been unlocked, to where labor cost discrepancies are not as great. Geopolitics also factors in, with more isolationist trends.
Technology continues to advance, for instance in energy production. However, it remains to be seen if the pace of development is able to stay ahead of load.