If you want a clear example of how Wall Street is making income inequality worse, stop and think about the cost of your next can of Diet Coke or Bud Light.

The New York Times reported this weekend, following up on a Reuters report from more than a year ago, that Goldman Sachs and other banks are making millions of dollars simply by moving aluminum around in warehouses for no apparent reason. This pointless busy work has raised the cost of the aluminum that goes into Coke cans, cars and house siding, costing the economy $5 billion in the past three years, according to various estimates.

Now, that is not very much money in the grand scheme of things, as Fortune's Stephen Gandel points out. And quirky commodities regulations may be at least as much to blame for this goofball state of affairs as are the banks and their relentless blood-funnel jamming.

But those caveats are beside the point. The point is that this aluminum juggling is as plain an example of what economists call "rent seeking" as you'll find. Rent-seeking is the fine art of milking of money from a market while not actually creating any new wealth or anything of value to an economy. In fact, it is an economic detriment: As the NYT points out, Wall Street's rent-seeking means consumers "pay more every time they fill up a gas tank, flick on a light switch, open a beer or buy a cellphone."

The other reason to care is because this rent-seeking has broader economic effects, one of which is widening the gap between the haves and the have-nots. As the Economic Policy Institute, a liberal think tank, pointed out recently, the soaring pay of bankers and CEOs has driven most of the rise in income inequality in recent decades.

There is no evidence that these bankers and CEOs are being paid so much more for all the extra value they are adding to the economy. Instead, the available evidence suggests they have been successfully rent-seeking, for the most part --- largely because regulators, in the name of free enterprise, have increasingly been letting them run amok in new markets, including physical commodities markets.

This runs contrary to the arguments of defenders of the 1 percent, such as Harvard economist (and former economic adviser to President George W. Bush and Mitt Romney) Greg Mankiw, who argues that the rich are richer because of all of the value they add to society.

But there is no apparent economic value in moving aluminum around all day with a forklift (OK, OK, maybe the employment of the forklift driver). Nor is there any economic value in manipulating commodity prices by jamming futures markets with fake trades, as a New Jersey high-speed trading firm called Panther Energy Trading was accused of doing on Monday. Nor in the estimated $83 billion discount the biggest banks get in their borrowing costs merely by virtue of their massive size. Nor in Libor manipulation or electricity-market manipulation or the many other markets banks are apparently just manipulating all the time.

All of it just skims cash off the top and leaves nothing in return.

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  • 10. Bank Of New York Mellon

    Total assets as of March 31, 2012: $300 billion. (Federal Reserve) (AP Photo)

  • 9. HSBC

    Total assets in the U.S. as of March 31, 2012: $340 billion. (Federal Reserve) (Frederic J. Brown/Getty Images)

  • 8. U.S. Bank

    Total assets as of March 31, 2012: $341 billion. (Federal Reserve) (Wikimedia Photo)

  • 7. Morgan Stanley

    Total assets as of March 31, 2012: $781 billion. (Federal Reserve) (AP Photo/Seth Wenig)

  • 6. MetLife

    Total assets as of March 31, 2012: $820 billion. (Federal Reserve) (AP)

  • 5. Goldman Sachs

    Total assets as of March 31, 2012: $951 billion. (Federal Reserve) (AP Photo/Richard Drew, file)

  • 4. Wells Fargo

    Total assets as of March 31, 2012: $1.33 trillion. (Federal Reserve) (AP Photo/CX Matiash)

  • 3. Citigroup

    Total assets as of March 31, 2012: $1.94 trillion. (Federal Reserve) (AP Photo/Mark Lennihan, File)

  • 2. Bank of America

    Total assets as of March 31, 2012: $2.18 trillion. (Federal Reserve) (AP Photo/Chuck Burton, File)

  • 1. JPMorgan Chase

    Total assets as of March 31, 2012: $2.32 trillion. (Federal Reserve) (AP Photo/J. Scott Applewhite, File)