An economist who went by the name of Moore lived through the depression, but his economic and mathematics were never really applied or developed. They, nevertheless, contained an important element of business economics called the product cycle.
Product cycles for a firm tend to follow a pattern of slow growth, faster growth, and slow growth reflecting the life cycle of acceptance, penetration, and maturation of single product.
When economists look at the product cycle they can do so at various levels of aggregation from the individual firm with one product right up to all firms, many with a multitude of products at different stages of their life cycles.
Overall for the whole economy, it is important that economists really understand the maturity distribution of the product cycles of the firms operating in their economy. Yet, you would be surprised how little research into product cycles at the aggregate actually is undertaken. Why could this be? Are the mathematics so difficult?
The answer is an aversion by teachers of economics for situational or historical analysis based on statistical theory that looks at progress of individual technologies and products forming the product cycles of economies and firms. Yet, these product cycles are at the heart of understanding the mathematics of the Stock Market, consumption and investment of an economy. Instead, economics training has separated itself from the real world and moved into mathematical conjecturing that not only is not easy to understand, but ultimately misleading.
I come from a school of thought that if you want to know how something works, you get to know everything about that something. This means that you study it's history. You look at the world economy as made up of millions of products that each have a history and you develop a mathematics that is suited to understanding those histories individually and in total. You do a form of product historical accounting. Distinct patterns do emerge.
In some industries you find that there is very little competition. This is reflected in the distribution of firms and products historically. These industries are at a definable stage in their life cycles reflected in the products of these industries that are predominately at definable stages.
Understanding of industrial cycles and business cycles go hand in hand. It has been popular among some economists to claim that business cycles no longer exist or are not that important. Such claims are fanciful!
What emerges is conflicts between the approaches of individuals coming to the table from different ends. Some try to look at the total without understanding the composition. This can only go so far. Others look at individual cases without looking at the total. Both approaches have serious shortcomings, and yet people continue to behave as though the shortcomings do not exist.
To be able to predict economic growth and real growth rates a balanced approach coming from both ends of the table is required.