Final answer:
Throughout 2012 to 2021, the United States is consistently classified as an economically developed country, experiencing ongoing economic growth, advanced industrialization, and high living standards, as reported by authoritative economic sources and institutions.
Step-by-step explanation:
The classification of the United States' stage of economic development from 2012 through 2021 consistently falls into the category of economically developed countries. Economically developed countries are characterized by strong industrialization, high levels of income per capita, advanced technological infrastructure, and a relatively high standard of living. Throughout these years, the U.S. maintained a mature and diversified economy which is indicative of its status as a developed country.
Despite various economic challenges, including the recession recovery and the more recent COVID-19 pandemic, the U.S. has continued to showcase its resilience with ongoing economic growth and technological advancements. This is supported by data and insights from institutions such as the U.S. Department of Commerce, the Bureau of Economic Analysis, the National Bureau of Economic Research, and the World Bank.
With respect to Economic Growth, publications such as the Economic Report of the President and databases like the World Bank's World Development Indicators continue to provide updated figures showing steady growth in the United States' GDP, among other economic indicators. The majority of countries in Europe, similarly classified, are in stage 5 of the index of economic development, which correlates to advanced economic statuses.