Nobody, that's who.
Just check out this excerpt from an article by Rex Nutting at Marketwatch and you'll see what I mean. The article is titled "No one is investing in tomorrow's economy":
The U.S. economy simply isn't investing enough to ensure that there will be enough good paying jobs for our children and our children's children. Net investment - the amount of capital added to our stock - remains at the lowest levels since the Great Depression. ...
Net investment...measures the additional stock of buildings, factories, houses, equipment, software, and research and development - above and beyond the replacement of worn-out capital. In 2012, net fixed investment totaled $485 billion, only about half of the $1.1 trillion invested in 2006...
If businesses, consumers and governments were investing for the future at usual rate, the economy would be at least 3% larger, employing millions more people. That's a huge hole in the economy that can't be filled by heavily indebted consumers, especially at a time when government is handcuffed by forces of austerity. ("No one is investing in tomorrow's economy", Rex Nutting, Marketwatch)