There are hundreds of people in the world whose names you might never know but who own millions -- if not billions of dollars.
These wealthy individuals often go out of their way to hide their assets from scrutiny -- sometimes from the public and sometimes from their own government.
Russians, for instance, are reportedly pouring record amounts of cash into London monetary markets to hedge against any future political retribution.
Figuring out how much money someone has is not an easy task.
Even Forbes magazine, which just came out with its annual list of the richest 400 Americans, acknowledges that its figures are just estimates and are "deliberately conservative."
"Most things like this are very private," says Daniel S. Hamermesh, an economics professor at the University of Texas at Austin. "People aren't running around telling people about their sex lives or marijuana consumption. They're considered private things in this and other countries. Income is something that is mine."
There are other reasons too.
Somebody -- maybe not a billionaire or even a millionaire -- might work at two jobs and doesn't want one employer to know how much the other pays. If the employer had that information, it might be less likely to dole out a raise.
Others might not want to be hassled by charities and others seeking donations.
Then, Hamermesh says, there are those that want to "beat the taxman."
"Look at Italy and Russia where this is a national pastime," he says.
This Forbes list only looks at the American wealthy -- everyone on it is worth at least $1 billion -- many own or have owned significant chunks of publicly traded companies. In that case, their ownership of such stocks is publicly disclosed.
Calculating the net worth of a Russian oil czar or a Saudi prince is a lot more difficult.
Stashing Cash Overseas
The influx of Russian cash is flowing into London, says John Coffee, a professor at Columbia University Law School, because of uncertainty.
"Putin some day will be out of power," Coffee says. "You don't know … on which side you'll be of his successor. And if you can have $100 million in London, you can live quite happily out of the country."
When England returned Hong Kong to Chinese control, Coffee says, a tremendous amount of cash flowed from Hong Kong to Singapore and Canada.
So why England?
"London is one of the deepest financial markets in the world -- quite possibly the deepest -- and it has almost no regulation," Coffee says. "You can invest in all different sorts of investments. You don't have to go through the same kind money laundering restrictions that the United States has."
Americans looking to hide assets from taxation or for other reasons have always looked abroad. Switzerland used to offer a high level of secrecy in its banks, but that has changed. Other countries, like Lichtenstein, have taken on that role. For Americans, the Cayman Islands and Bermuda are popular places to shift assets.
Generally, assessing somebody's wealth abroad is much more difficult than in America.
"What the Saudis or what some of the Russian oil plutocrats own," Coffee says, "is all a matter of very, very approximate calculation at best."
The Trouble Calculating Worth
But even in the United States there is very little information about how much the super-rich in general earn.
Hamermesh says the federal government's income surveys stop at $150,000 a year.
"We have very, very bad information on the income of high-income people," Hamermesh says.
There are a lot of public records and ways to find out what somebody is worth, but unless you have access to somebody's bank account you can't know it all.
Forbes says it goes through Securities and Exchange Commission filings, court records and calls analysts, employees, competitors and even ex-wives.
"We do not pretend to know everything on a private balance sheet," the magazine states when explaining its methodology.
Forbes says it tries to include everything, from stakes in publicly traded or privately held companies, to real estate, art, yachts and mansions.
But in the end, it's an educated guess. When Forbes says somebody is worth $7 billion, it means that the person is worth at least $7 billion.
How to Shield Assets
So what are some ways that the rich can shield their assets?
Michael J. Zuccarini, a partner with Smith & Zuccarini, a law firm near Seattle that does tax, business and estate planning, says that one of the best ways is to set up a revocable living trust.
Putting assets in such a trust doesn't always shield them completely, but makes them harder to find.
Zuccarini says that many trusts are set up in somebody's initials. So, for instance, if you were searching for Bill Gates in a computer database of land records he wouldn't show up because the property might be under the name of the B.G. 2007 Trust.
Zuccarini says the biggest disclosures often don't come until a wealthy person dies.
Most states require a will to be filed in court, even if it doesn't go through the probate process. Additionally, some states require a detailed inventory of assets.
The wills of many celebrities have been made public this way, and some can be found on the Internet.
Court TV has an entire section of its Web site dedicated to the wills of famous dead people, including Jacqueline Kennedy Onassis, Babe Ruth, Richard Nixon, Elvis Presley, John Lennon, Dorris Duke, Jerry Garcia and Marilyn Monroe.
But putting assets into a trust can preserve that financial privacy, even after death.
Another vehicle some rich people use to shield their assets from scrutiny is to set up a limited liability company.
Zuccarini says that confidentiality is one small reason to set up a trust. Many of his clients do it for a bevy of other reasons.
But those who do create trusts however, don't want others to know that they have a trust. So while all of somebody's money might be in the trust, Zuccarini says his clients don't want the trust's name on their checkbook.
"I do have a quite a few clients who don't want their neighbors to know how much money they have," he says. "One of the major reasons: They want people to change their view of them. Many live modestly."
There is one more reason.
"People are afraid of being sued," Zuccarini says. "The more people that know they are worth a lot of money, it's like running around with a target on their chest."