Dow propelled by one stock

The Dow Jones Industrial Average is at record highs and it's mostly because of just one of its components.

Caterpillar is doing a lot of heavy lifting when it comes to moving the Dow index, a huge change from last year when it was up just 1 measly percent against the Dow's 26 percent gain.

Though it's just 4 percent of the entire average, the equipment maker is up nearly 17 percent this year. To put it in perspective, Caterpillar accounts for more than half of the entire Dow's gains. And, were it not for Caterpillar, Merck and Disney, the Dow would be down in 2014.