In 1919 the Weimar government initiated a massive 'investment' boom by abandoning all monetary controls. The results were spectacular. An average of 30,000 firms set up in each of the inflation years. The capital goods industries boomed, activity in the finance sector exploded and rampant speculation became the norm. By the end of 1923 the country was an economic ruin.
Economic history is economic theory's laboratory.
That so few economic commentators use it is a disgrace. Of those that do use history, only a few seem able to correctly interpret it. This is equally disgraceful.