2 Stock Ideas from Bill Gates' Portfolio

When it comes to the stock market, many investors -- myself included -- spend quite a bit of time analyzing the trading activity of the richest and most successful investors in the world. These include well-known experts like Warren Buffett, Carl Icahn and George Soros, who have become bona fide billionaires as a result of their successful investing strategies.

No matter how successful or rich these mega-investors are, they're still far less wealthy than Bill Gates -- the richest person in the United States, with an estimated fortune of $59 billion, according to Forbes.

Most people know Gates' wealth stemmed from founding software giant Microsoft (Nasdaq: MSFT), as opposed to successful stock picking. What is less well known is that Gates has shifted a good deal of his wealth to the Bill & Melinda Gates Foundation Asset Trust, which funds the Bill & Melinda Gates Foundation, his family's main philanthropic vehicle, which focuses on solving health care, education and poverty issues worldwide.

The trust manages not only Gates' contribution to the endowment, but also donations from various other wealthy individuals, including Warren Buffett, who contributes annually. The foundation currently sits on an estimated $15 billion in capital, which the trust strives to preserve in order to serve its philanthropic goals.

Even less known is that Gates has a private investment company, Cascade Investment LLC, which he uses as a vehicle to diversify his wealth out of Microsoft and explore other opportunities in the stock market.

Clearly, Gates knows how to invest his money. So when he buys or sells a stock, you need to pay attention. It could lead to a solid investing idea worth adding to your own portfolio.

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In the fourth quarter of 2011, for instance, Gates was busy buying and selling an interesting group of stocks. Here's some insight on two of the billionaire's latest investment moves...

A long-term commitment to Ecolab
At the end of February, cleaning product giant Ecolab (NYSE: ECL) named Gates' close business confidante Michael Larson to its board of directors.

Ecolab makes and sells cleaning, sanitizing, pest control and maintenance products and services to major hospitality, health care and industrial facilities throughout the world. This work cannot be cut in an economic downturn, which results in an operational consistency that probably helps the managers of the Cascade and Gates Foundation portfolios sleep well.

Cascade owns a sizable chunk of Ecolab -- 27 million shares, or roughly 9% of the company, for a total market value of about $1.6 billion. The Gates Foundation is another big holder. It ended the year with 252,000 shares, a year-end market value of $4.4 billion.