BANK OF AMERICA: Avoid these 20 stocks heavily owned by just a few investors, since they're especially vulnerable to market turbulence going forward

• Savita Subramanian, the head of US equity and quantitative strategy at Bank of America Merrill Lynch, has identified the companies in the S&P 500 that have a high concentration of ownership by just a few people or firms.
• Subramanian wrote that those companies are at risk for large downturns, as they could go through more volatility than those with more ownership that's more evenly distributed.
• BAML devised a "concentration index" to help identify the companies most at risk for that kind of volatility. It's based on how much of their stock is owned by just 10 shareholders.
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Companies want their biggest shareholders to support them enthusiastically, but there might be such a thing as too much love.

Savita Subramanian, the head of US equity and quantitative strategy at Bank of America Merrill Lynch, recently highlighted a group of companies where a small group of shareholders owns outsize stakes. She wrote that such overly-concentrated ownership is a potential liability.

That's because the stocks could suffer major losses if a few of those owners, or even just one, decides to sell their holdings. With volatility on the rise and company earnings on the way this month, BAML suggests investors should be aware of that vulnerability.

"These stocks are likely to experience more volatility than those with a more diversified ownership base where different investors may have different 'sell disciplines,'" she wrote.

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Subramanian and her team identified the stocks that face most risk in two ways: By tallying up the percentage of each stock held by each company's 10 largest shareholders - above 50% for all of the top-rated companies - and by calculating a number called the Herfindahl-Hirshman index, which is used to measure concentration.

The higher that index score is, the more concentrated the ownership. Here are the 20 S&P 500 companies with the highest scores, ranked in increasing order: