The rule suggests trouble: the index has fallen at an annual rate of more than 2% in the past six months.

ECONOMIST: Leading economic indicators

Actually, the historical performance of Athens General Exchange Index confirms this rule.

FORBES: Four Flavorful Tastes Of Greece To Ride The Rebound

The index evaluates economic freedom by looking at the rule of law, regulatory efficiency, the size of government and open markets.

BBC: Hong Kong retains top spot of world's freest economy

The Index evaluates countries in four broad areas of economic freedom: rule of law, regulatory efficiency, limited government and open markets.

CNN: Which country has most economic freedom?

As a general rule, Bill Palmer, a certified financial planner at Win Wealth Management in Denver, prefers index funds or exchange-traded funds for their lower fees.

WSJ: Investors Buying Dividend Stocks for Income Are Taking On a Lot of Risk.