Stock prices have declined about 9 percent this year, and it's only January. The good news is that everything the typical saver needs to know to safely navigate the tumult in the global financial sector fits on the four-by-six index card shown above.

At a time like this, this card is more significant for what it doesn't say than what it does. You might notice that there's nothing in those 24 square inches about worldwide collapses in stock prices.

Instead, the card lays out a simple strategy — point by point — for ordinary, Main Street investors to follow through all the economy's ups and downs.

In other words, stand by sound investing principles and resist the temptation to panic and sell, advised Harold Pollack, an expert on personal finance (among other things) at the University of Chicago.

"You should not be doing anything different in times of financial turmoil," Pollack said. "All the evidence is that this is a great time to do nothing."

Pollack is the author of this index card, along with a newly published book called "The Index Card," which he wrote with journalist Helaine Olen. Wonkblog has covered his financial recommendations in the past — most recently, in the summer, which was the last time stock prices plummeted.

The advice on the card, which is based on the past few decades of economic research into the nature of stock markets, is pretty straightforward.

First, save money. Saving 20 percent of your money as the card instructs, is a good goal, though Pollack acknowledged it might be unrealistic for many families when median household incomes have been declining for 15 years.

Then, put your savings in accounts that will save you even more money in taxes, such as a Roth individual retirement arrangement or a 529 account for college tuition.

Once your money is in those accounts, use it to buy index funds, what Pollack calls a "vanilla ice cream" way of investing conveniently and inexpensively in a wide range of stocks or bonds.

With these funds, your investments will gain and occasionally lose value at roughly the same rate as will the market as a whole.

Don't try this at home

Some savers might want to try to get better returns by reading the stock pages in the paper, listening to financial news on cable television and picking the companies they think are likely to do well. Or they might try to beat the market by buying when they think prices are going up and selling when, like now, things start to look bad.

Mathematically, these people are almost certain to fail. You might not be happy when, as for many savers this month, your statement from the bank is covered in red ink. The fact is, though, it's nearly impossible to do any better on your own.

To see why, think about how the markets work. Big financial institutions are staffed by people who spend all day thinking about whether the price of a stock or a bond accurately reflects how much it's worth.

If the people at one institution think a certain company has hard times ahead, they'll sell that company's stock. If people at other financial institutions agree, they'll sell the stock, too, and they'll bid the price down.

On the other hand, if things are looking up, the people at those financial institutions will buy the stock, and the price will rise. As a result, at any point in time, the price of a stock represents the opinion of legions of financial experts about how much the company is worth.

If you're going to buy or sell, you had better be sure you know something all those people don't.

"Market prices are basically determined by the collective action of a very large number of very sophisticated investors, for whom this is their full time job," Pollack said.

That's true even when prices are plummeting. "When you are selling out, you are basically saying, 'I believe that the stock market is worth less than all of these other people believe it is,'" he added.

Don't be a hero

There might be a few people out there who are capable of consistently beating the market. (You know who you are.) As a matter of arithmetic, though, there can't be too many of them. If there were, their decisions about what and when to buy and sell would start to affect prices in one direction or the other.

As for the rest of you: Don't try to be a hero. Buy index funds.

With index funds, the price of your investments will sometimes fall. Over the long run, though, they will rise. That's especially important to remember during a collapse in prices.

"If you precipitously sell, the historical record suggests that you often miss the rebound that happens," Pollack said. "You’re basically selling when the market is at its minimum."

"Think of what happened to the people who sold their holdings in 2008," Pollack added. "Those people lost out on a tremendous run up in the stock market." Indeed, in the seven years since the stock market's nadir in early 2009, prices have doubled and then some, even after this month's declines.

Occasional collapses in the stock market, like this one, tend to be more drastic than in the bond market. Over the course of a few decades, though, the stock market has historically produced greater returns, more than making up for those losses.

For older people, who might not live long enough to enjoy the benefits of investing in stocks over the long term, it makes more sense to put money in bonds. For younger people, stocks are a better bet.

Pollack's rule of thumb: Subtract your age today from 110 to find the percent of your money you should invest in stocks. Another approach is to buy a target fund, a type of index fund designed for everyone planning to retire in a given year, that combines stocks and bonds in the right proportions for people in that age group.

Know your financial adviser

If this isn't the advice your financial adviser is giving you, then you should make sure you know where your adviser's bread is buttered. Many advisers receive commissions from banks when their clients buy the banks' financial products, even if doing so isn't in the clients' best interests.

Pollack argued that you should be the only one paying your adviser. He added that you should make sure your adviser has committed to a fiduciary standard in all their transactions with you, meaning the adviser is legally obliged to put your interests first.

Wall Street disagrees. Lobbyists for the financial industry have been working hard against a proposal by the Obama administration to bar banks from paying commissions to financial advisers to sell their products. The administration's opponents argue that most savers don't have enough money to pay a financial adviser's fees by themselves, and that commissions from banks — even if they cause conflicts of interest — help pay for financial advice for many people who couldn't otherwise afford it.

From Pollack's point of view, your adviser's fees are worth the money if he or she has committed to a fiduciary standard. In any case, all the financial advice you really need fits on an index card.

Pollack produced the video below. It explains the idea of a fiduciary standard, with cake.