With enough wealth and political power it is possible for a group of very wealthy individuals to take over all governments and dictate government policy. Once this is accomplished, it is easy enough to dictate policy to central banks which are arms of governments. It then becomes policy to maintain and elevate stock prices in order to please powerful and wealthy constituents.
Again, any economic or political issue can be explained in a few sentences and in common language. The Fancy models and complex statistics evolve because the solution is unpleasant.
This kind of system does not depend on formal groups and public decisions. Individuals and entities with common goals and interests find one another naturally. There need be no formal conspiracy. Government tampering with the stock market started during the Reagan administration. The practice has increased steadily from then until know. Using government to manage stock prices has been so profitable that the private market for trading stocks has largely disappeared. As long as the public does not object or until both our economy and form of government are destroyed the asset enhancements will continue.
There are countless reasons why this kind of activity will destroy the economy. I will mention just one. The free market system is built on an uninterrupted system of out with the old and in with the new. Rigging the stock market destroys that natural process and the old disappears without anything new taking its place. I will also mention that unearned money corrupts the rich just like it does anyone else. The rich are naturally innovative and industrious. Laziness becomes the rule and productivity falls.
These days, the stock market never goes down because all kinds of algorithms have been developed to move it higher and keep it from dropping. The same moneyed interests which control government and central banks, also control the news media. The rich now have a way to profit endlessly by just having the government goose the stock market, effortlessly making unfathomable sums of money.
Don’t misunderstand, the rich are not purposefully trying to impoverish everyone else. They are just going after their hoggins. The poor and middle class just happen to be standing in the way.
The markets will go up until the system fails. That could be today, tomorrow or a number of years.