Market bubbles involve rapidly rising prices that suck in buyers hoping to make money quickly, who carry out little due diligence and don't worry much about the long-term prospects of what they're buying.

Standard valuations are always dismissed as no longer relevant. And the bubble is usually inflated by cheap money. Sound familiar? Welcome back to the Everything Bubble, complained about for years mostly by investors concerned about a Federal Reserve stuck on easy.

Except, the Everything Bubble is in the imagination of the many investors complaining about it. First, it isn't everything. Second, it isn't a bubble (although some individual stocks -- I'm thinking of you, Tesla -- are in mini-bubbles).

The not-everything part is obvious: Oil stocks are in a terrible place. Retailers are going bust in droves. Banks are still down 30% this year in the U.S., and are worse in Europe. Travel and tourism stocks are in a hole. Smaller company stocks have rebounded, but only back to where they stood in January 2018. The worst-rated junk bonds have missed out on easy money entirely, with their yields rising this year. This isn't indiscriminate buying of everything.

The argument against this being a bubble is more contentious, with the S&P 500 hitting a new high on Tuesday amid recession and the breakdown of the geopolitical order.

Don't get me wrong, the signs of excess are impossible to deny. Most obviously, the S&P's forward price/earnings ratio is back up to where it stood in October 1999, just months from the peak of the dot-com bubble.

Bubble proponents like to think of this as driven by the vast amounts of money central banks are creating. It has to go somewhere, so it floods into assets where investors feel comfortable: stocks with decent prospects, bonds of governments backed by those central banks, corporate debt with decent security, gold.

There's some truth to this. Central-bank buying pushes investors into other assets while government subsidies have -- at least until the recent cuts to U.S. benefits -- boosted household income.

But I prefer to think of what's going on as driven by the competing forces of the price of money and the economic outlook, rather than the amount of money.

Lower interest rates help all assets, filtering through from Treasurys and corporate bonds to risky shares. All else equal, a stream of future income is more valuable with a lower interest rate. The competing force that makes all else not equal is the economic outlook: central banks and governments are in emergency mode because the economy is in crisis.

The two forces don't balance out evenly. Treasurys are sensitive to the outlook for interest rates and inflation, not economic growth, so they benefit from cheaper money and don't suffer from the economy.

Shift down the spectrum of corporate bonds from best to worst, and they become less and less sensitive to rates and more and more sensitive to the economy. This year the point where higher default risk more than offsets lower rates is in the middle of junk at credit rating BB. At BB or below, yields are higher than at the start of January.

A similar calculation can be made for stocks. Lower rates mean profits further in the future matter more to the share price, so companies with steady earnings no matter what the economy does are worth more. Those that are sensitive to the economy are worth less, because future earnings are expected to be hit. Growth stocks do incredibly well, because their future earnings are expected to be higher and, at least for those thought immune to economic weakness, worth more as well thanks to lower rates.

Apply this framework and there's no bubble. U.S. stocks are more highly valued than in the past because they are dominated by big growth stocks, themselves justifiably more highly valued thanks to low rates.

Investors have discriminated between winners and losers even within the traditional growth stocks: online retail wins with both more customers and lower rates, but internet taxi companies such as Uber Technologies lose despite lower rates as customers vanish.

Internationally investors have discriminated too. Foreign markets mostly have fewer growth stocks, leaving them suffering more from global economic weakness than they benefit from lower rates. Notable among the losers is the U.K., suffering from one of the biggest Covid-related economic falls, from Brexit and from a stock market skewed at the start of the crisis to banks and oil.

The market could still be wildly wrong in its various Anti-Covid trades. Overall it is pricing a weak economy propped up by never-ending support from central banks. If the Fed signals that it won't keep throwing everything at the economy at the first sign of weakness, the current prices will make little sense. Similarly, if the pandemic recedes and the econo