Sys­tem dy­nam­ics and sta­bil­ity (SAS)

In macroeconomics, there are many models that link interest rates, unemployment, economic growth, etc. They can be used to decide on stimuli. Here we examine the relatively rarely asked question whether these models are stable, i.e. whether a small deviation from equilibrium leads after a short time to an at least similar or completely different equilibrium. In the latter case, control via e.g. key interest rates would be completely pointless.
 
It has been shown that as soon as a relatively small proportion of speculative profits flows into the real economy, a stable equilibrium no longer exists.
 
In a second part, a Fourier analysis was used to show how the speculative value of a share can be measured relatively easily. The spectra of the nearly 3,000 shares examined also show that the theory of market efficiency of Eugene Fama (Nobel Prize 2013) cannot be correct.