When the financial markets started to perk up in the last few weeks of 2011 it was easy to see what was driving the turnaround: good economic news out of the US, and a shedload of cheap medium-term loans for banks from the European Central Bank.
Since then there has been more good news from the real economy - especially in the US but also the core Eurozone economies and the UK.
The impact on stock prices is plain for all to see - and, possibly temporary. The implications for central bankers are more complicated, but they will be hanging over them for some time to come.
First, those soaraway stock markets. There have been some market wobbles this week, thanks to Greece, but the FTSE 100 is still more than 5% up on the end of 2011, and nearly 17% on its low point in mid-August.
The key American index - the S&P 500- has gained 6.5% so far this year, and more than 20% since October.
As you know, bond prices (and the implied cost of borrowing for governments) have also reflected the better mood - at least if the government in question is not Portugal.
Italy's cost of borrowing is now around 5.6%, the lowest it has been since October.
The interest rate on US government debt has actually crept up slightly in recent weeks. But in case you were wondering, that is good news as well. The rule of thumb here is that if your long-term interest rate, or bond yield, is exceptionally low - it's good news if it goes up. But if it's high, you want it to go down.
So, we want the Italian yield to fall, because that would suggest that investors see less chance that Italy will default, and more chance that the Italian government will be able to find buyers for its debt, with all this cheap bank liquidity sloshing around.
But we also want the US long term rate to go up, because that would suggest that investors expect the US recovery to be stronger than previously thought, and the world economy slightly less frightening.
Got it? Good. Now let's turn to those poor central bankers.
I say poor, because, to some extent, the better the economic news, the harder their job gets - at least when it comes to the Eurozone and the US.
The ECB, for one, will be deeply uncomfortable with being given so much credit for the upturn in global sentiment.
Remember they weren't supposed to be playing the "lender of last resort" for hard-pressed Eurozone governments. Yet, somehow, the financial markets have decided that they have done just that in providing these cheap three-year loans.
The latest ECB survey of lending conditions, carried out AFTER that medium-term cash for banks, suggested that banks are now even less keen to lend to European companies than they were a few months ago. The majority were expecting to cut the supply of business loans, mortgages and consumer credit in the first few months of 2012.
So, there's no evidence - yet - that the ECB lending is set to ease the crunch on the real economy. But that hasn't stopped investors believing that it will ease the crunch for Eurozone governments under pressure. If you're the ECB, that is not exactly the combination you were looking for.
There's a lot more to be said on the question of who is being bailed out by the ECB lending - and what will happen next. Suffice to say that trusted experts like Morgan Stanley's Huw van Steenis are expecting banks to hoover up another 150bn-400bn euros in medium-term funding from the ECB at the second offering at the end of this month.
The Eurozone feels like it is in a safer place now than it was at the start if December. But the same probably cannot be said of the ECB. They are up to their necks in "last resort" lending, for the duration.
The problem for the US central bank is somewhat different. Recent data - particularly Friday's news on the labour market - suggests that something is going surprisingly right with the real economy. So right, in fact, that if it continues, the gloomy forecasts for 2012 might have to be ripped up.
This, naturally, is good news for the US Federal Reserve. Except, it comes after the institution released its first ever long-term forecasts for interest rates, and stated that it expected rates to be at their current historic low rate until at least the end of 2014.
If some kind of tide has been turned (and it is early days yet) - and if the US can really "decouple" from the Eurozone's troubles, as so many in the business community now seem to believe, then things could look rather different for the Fed in 6 months time.
Then, keeping US short term rates near zero until the start of 2015 could start to seem seriously over the top. And the Fed would face the delicate job if explaining to market traders that the short term rate they had been plugging into all their algorithms was variable, after all.
There's a prayer for President Obama coming out of this; "Lord give me good news on the economy - but not so much good news that the Fed has to bring the financial markets back to earth this side of polling day."
Which leaves us, finally, with the Bank of England, and its eagerly awaited decision on Thursday, whether to continue injecting more money into the economy or put the policy of quantitative easing back on hold.
Expectations on this front have fallen somewhat, on the back of some strong survey data, most recently from the manufacturing sector.
For what it's worth, I think another sizeable dose of QE (£50-75bn) is more likely than not. After all, the most recent, November forecasts showed inflation falling well below target - even after the £75bn agreed in October had made its way into the economy.
Overall, the news since then has not suggested that inflation will be higher than forecast then - or the economy much stronger. Quite the contrary: the average private forecast for growth in 2012 has tumbled from 1.5% to less than 0.5%.
That, too, may turn out to be an over-reaction - or at least behind the curve. But the betting must be that the Monetary Policy Committee will step up to the plate this week. Just don't expect them to enjoy it.
