According to Goldman Sachs:
http://www.zerohedge.com/news/2013-02-19/goldman-explains-market-best-not-look-gift-horse-mouthA solid rally today and new cycle highs for US equities – but that’s where the story stops. No obvious catalyst. No bullish data. European stocks traded well, with most people pointing to a better German ZEW print, but it’s not clear why that would translate into such a strong US trading session. Maybe it’s best though not to look a gift-horse in the mouth.
WallStreetOasis has three theories:
http://www.wallstreetoasis.com/blog/djia-new-cycle-highs-wait-what-my-theories-on-the-current-market Europe is Better: Maybe Europe is better than we all thought. Perhaps Spain actually has a debt to GDP ratio of 85.3%, and that number is totally right and probably fine, as opposed to totally contrived nonsense trying to hide a far worse picture.
The Current Season of The Bachelor is Driving Economic Growth: Week 7 of The Bachelor attracted nearly 400,000 more viewers than the previous season, which is clearly translating into stronger consumer spending in the US. Is this actually a very likely scenario? No, it's absurd, it's just more likely than Europe being healthier.
Massive, Coordinated Central Bank Intervention in Developed Economies: As we're all familiar, the Federal Reserve, the BOJ, the BOE, the PBOC, and the ECB have all been engaged in sterilized and (recently) unsterilized market actions. Since the money, as you all know, has to go somewhere, why not equities?
In other words, what we're seeing now are The System's levers being pushed to "11" to keep it afloat... My theory? It's an opportunity for those people who 'get it' to get out while the getting's good (and equity prices are high).