The Dow Jones Industrial Average (DJINDICES:^DJI) is up 221 points today. America didn't trot right over the fiscal cliff like a hapless lemming, so there's hope of economic growth in the new year.

But you might be surprised to learn which stocks actually moved the Dow the most today. The market movers aren't always who you might think, thanks to the various weightings of our most important indexes. The Dow happens to be weighted by share prices, and that detail has serious implications.

Hewlett-Packard (NYSE:HPQ) won the race for the biggest single-stock jump. The tech giant has gained 4.7% as management admitted that it might be necessary to sell or spin out some of the less profitable cogs in the complicated HP machine. But that move added just five points to the Dow's overall value.

HP's minuscule share price limits its Dow-moving power. Rather, the biggest Dow contributors were high-priced stalwarts IBM (NYSE:IBM) and Caterpillar (NYSE:CAT). Big Blue gained 2%, or 30 Dow points, and Caterpillar added 28 points by rising 4%. Together, these two stocks accounted for 26% of the Dow's total gains.

You could certainly argue that these tickers deserve to make a major impact on the market's premium index. Caterpillar is the Dow's closest proxy for the manufacturing and construction sectors, which will benefit greatly from the aversion of a fiscal-cliff disaster. Meanwhile, the black cloud hanging over future corporate IT budgets just rolled away, which is great news for IBM. But then, Microsoft (NASDAQ:MSFT) also jumped 2% on the same news but added just four points to the Dow.

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