By The Book:
Personal incomes and consumer demand for goods and services dropped rapidly during the Great Depression of the early 1 930s, thrusting marketing into a more important role. Organizational survival dictated that managers pay close attention to the markets for their goods and services. This trend ended with the outbreak of World War II, when rationing and shortages of consumer goods became commonplace. The war years, however, created only a pause in an emerging trend in business: a shift in the focus from products and sales to satisfying customer needs.
The marketing era is after the 1950s when less emphasis was placed on producing and selling goods and more was placed on what the customers wanted and needed.