There is a real-estate / state government sourced investment bubble in China ATM.
In short, the Chinese federal government sets GDP growth targets for each and every state. Every state is therefore obligated to meet these targets. Post 2009, real GDP growth has been underperforming, and more of the remaining GDP has to be made up for in infrastructure spending (which includes building apartments, airports, and the usual roads, bridges rails etc on debt). This is visible in various "ghost" cities and malls which have popped up recently (in addition to undercapacity airports and elaborate train stations). This in itself isn't necessarily a problem. The problem comes in when increasingly, a large amount of the money the states are lending is coming from "shadow loans" (unregulated black-market loans, analogous to sub-prime mortgages (kindof)) because regular forms of more legitimate financing have dried for these purposes (too much infrastructure already).
This is simultaneously fueled by difficulties rich Chinese have in being able to invest abroad, leaving condos in these ghost cities being owned, and purchased by investors' excess capital as assets (similar to a real estate bubble as what happened in Dubai a few years ago).
This excess capital, sourced from underperforming Chinese states leaking over to other markets, have been responsible for local real estate bubbling over in major cities like London, Vancouver, San Francisco, New York, etc by foreign nationals buying these properties as investments as a way to shelter money. It's very likely this capital is also indirectly being displayed in public equity markets.
(note: this is my own analysis of several articles and reports I read, so take it with a grain of salt)
I know nothing about finance but the Federal Reserve has provided new money at almost no interest to banks for a fairly long period of time from ~2008 onwards (this was called quantitative easing). This essentially forced the EU and countries like Switzerland to do the same, if they did not want their currency to get too strong. It is not a stretch of imagination that this fueled much of the current stock market boom, both Euro and Dollar have lost a lot of value at roughly the same pace.
Yeah, the fed loans money to banks at, essentially, zero interest, and the banks then use it to invest in the stock market, or some such. They make money, because the market isat all-time highs. They pay back the fed, and keep their profits.
All the major firms do this. It's nuts, but our government literally lends free money to investors on Wall Street so they can make millions of dollars on trades.
Of course, this all comes tumbling down when the markets are in bad shape. And, unlike most people in this thread, I fully expect any and all bubbles to burst due to some outside influence: Ebola, 9/11, war, etc. Something big happens to scare the markets, and the big party here in the Valley is over. Who know when that will happen, but it feels like the next year or so will be the time frame, if my gut is any indication.
This is interesting. Could you elaborate on some of the other sub-bubbles? Not being facetious, am really curious.