Spurred by the central bank, banks ease credit, massive borrowing and speculation begin that leads to fast growth of the economy. However, a lot of this growth is built on sand and is unproductive and reliant on continuing easy credit. Businesses and individuals take up debt they can't pay and invest in properties and ventures that produce little income. Banks rake in passive income and themselves borrow massive amounts of money to gamble in the booming stock/housing market.

Eventually, the steam runs out as interest on debt becomes too great compared to unproductive investments. This leads to bankruptcies and defaults. Companies and individuals are unable to repay debts and so are banks. The bust occurs.

The economy crashes. Mass defaults ensue. However, the central steps in and bails out the big banks and corporations through quantitative easing. They create money to buy up the bad assets and save the rescue them from collapse. The common citizen and smaller companies not in the globohomo band of brothers get the shaft.

They lose their houses and assets. The big corps and banks saved by the central bank come in and buy these up. Thus, they grow larger than ever before. The cycle starts anew as the banks spurred by the central bank begin another round of monetary easy to ''stimulate the economy" or "recover from the recession"

I am no economist but this is my rough understunding of the boom-bust cycle.