Markets around the globe -- beginning in Asia, where the Shanghai Index dropped 4.27%, continuing through Europe, where the FTSE 100 lost 3.10%, and ending in the United States, where the S&P 500 has already plunged nearly 3% -- fell today.

The bearish action was sparked when the Conference Board revised its leading economic index for China down from 1.7 to 0.3 percent. The Conference Board had initially released its index on June 15, but it had to retract its announcement and release an updated number because the previous number had a calculation error in it.

You may be wondering, what is the Conference Board and why does its Chinese index matter so much? If so, you're not alone.

Looking back to the world financial meltdown, it was the China market that led the market rallies around the world. Pretty much the rallies continued throughout 2009.

Beginning in January, markets in China and other developing countries started to sell off. The Shanghai Composite index fell below its 200-day moving average. This is the average of the preceding 200 days' prices. The BRIC countries (Brazil, Russia, India and China) markets are trading below their 100-day moving averages.

The global recovery is underway, and that's goods news for Cummins, Inc. (NYSE: CMI), which is why reiterating my Buy rating for the company's shares, first recommended on April 3, 2009 at a price of $29.70. If you bought CMI in April, you're up an impressive 57%.

Look for Cummins, with more than 50% of its revenue derived from international markets, to register an impressive FY2010 revenue gain, on sales gains of its efficient truck engine and infrastructure-based power generation equipment. Basically, institutional investors (IIs) have looked beyond CMI's FY2009 revenue decline, and have bid-up the company's shares since March, on the U.S./global economic recoveries.

Well, isn't this a fine kettle of fish. A year after the bankers, with their greed and excessive speculation, took world economies to the brink of chaos, they are complaining that regulating them is not a good idea.

Josef Ackermann, chairman of the Institute of International Finance, said: "There's a trade off between maximizing stability of banks and optimizing growth of the real economy."

To say the least, this has been one interesting and turbulent week for the stock market. We saw international markets crash for two days, severe down action, a three-quarter point emergency interest rate cut by the Fed, a $7 billion mistake in France and work on a rebate package in Congress.

It can be a little hard to understand international markets and how they all work. But allow me to use an analogy to explain their interaction.

We all grew up in a family, and one of the most important people in the family is Mom. Mom does a lot of work -- making meals, doing laundry, cleaning the house and even working outside of the house. Families can have very complicated interpersonal dynamics in them. There is a saying that "if Mama ain't happy ... nobody's happy." And I think there is some major truth to it.

But it applies to international markets as well. The U.S. market is the "mama" and the most important player. The $13 trillion U.S. economy is bigger, stronger and more dynamic than each of the other markets, and if it has troubles, other markets have troubles as well.