Three years ago, a client came to financial adviser Sammy J. Grant with a $500,000 portfolio. The man didn't work at Home Depot Inc., but 85% of his portfolio was in the company stock.

The investor lived in Atlanta and liked Home Depot, which is based there and has a strong presence in the community. Fortunately, Mr. Grant said he persuaded the investor to diversify the portfolio before the stock plummeted.

The scenario isn't unusual. While many consumers invest too much in one company because they have inherited the equity or collected it from an employer, individuals frequently overinvest in local companies. They drive by a company's headquarters, have neighbors who work there and believe it's a sound investment.

They think they're reducing risk and optimizing gains by following the adage, 'Invest in what you know.' Yet too much concentration in one stock actually increases risk as a lot of investors in Home Depot, Starbucks Corp. and Washington Mutual Inc. have discovered. Fortunately, this is a good time to diversify your portfolio. Stocks prices are down, and the federal tax rate on long-term capital gains is the lowest it may be for a long time.

'It is a well-known phenomenon,' says Stuart Ritter, a financial adviser at T. Rowe Price Group Inc. in Baltimore, Md. 'We think we know more about things that we're familiar with.'

David Hirshleifer, a finance professor at the Paul Merage School of Business at the University of California, Irvine, says people have a natural tendency to like things with which they're familiar.

'We treat things we're used to as friends,' he says. As a result, investors buy local stock and donate to local charities. That same sense of familiarity also encourages people to invest too much in their own countries rather than to build an international portfolio.

Conversely, investors are suspicious of companies they don't know, says Bing Han, a finance professor at McCombs School of Business at the University of Texas at Austin.

'You think too pessimistically about the returns on something that's not familiar,' he says. 'Since you don't know about it, you think it's riskier.'

That's why time and again investors purchase stock in local companies even if they have never looked at these companies' bottom lines. Ironically, going with what they think is safe has the opposite effect. A concentration of more than 10% in one holding makes their portfolio riskier.

'Generally, people hold on to a concentrated position because they think certain stocks will outperform over the long term,' says Ed Munshower, managing director and global head of the Tailored Portfolio Group at Citigroup Inc.

But a report released earlier this year by Citi found that a portfolio should have 25 to 30 stocks to minimize stock-specific risk. It found that only one in 10 stocks consistently outperformed the Standard & Poor's 500-stock Index over the past 20 years in any three-year period. Additionally, a third of the stocks in the index underperformed the overall market by at least 15% or more at any given year.

Mr. Munshower says it isn't unusual for high net-worth and ultrahigh net-worth clients to have high concentrations of one stock in their portfolios. 'It's very hard for people to sell a concentrated position,' he says. Sometimes, he says, it's an emotional attachment, 'but you have a perfect opportunity to take a concentrated portfolio and diversify it right now.'

That's because the market is down and the current capital-gains rate of 15% will very likely increase no matter who is elected U.S. president.

Financial advisers disagree on how quickly to diversify a client's holdings. Some professionals like to sell the assets immediately; others like to diversify the portfolio at regular intervals over a number of months or more.

'We've had people come in with a stock that's 20%, 30%, 40%, 50%, 60% of their portfolio,' says David Kudla, chief executive of Mainstay Capital Management, an investment-advisory firm in Grand Blanc, Mich. 'We try our very, very best to convince them that they need to diversify over time.' Sometimes the investors have worked at the company or inherited the stock, but often their holdings reflect the fact that 'they know people who work there.'

And in Michigan that unfortunately means many people have too much invested in the now poorly performing auto industry.

Jilian Mincer

三年前，有位客户来找理财顾问赛米•格兰特(Sammy J. Grant)。他有价值50万美元的投资组合，其中85%为家得宝(Home Depot Inc.)的股票，而他并不在家得宝工作。

他住在亚特兰大，那里是家得宝的大本营，他喜欢家得宝，这家公司在当地的社区形像非常好。格兰特说，幸运的是，他说服这位投资者在该股大跌前脱手一部分换成了其他股票。

这种情况并不少见。许多消费者在某家公司的股票上投资很大是因为他们是从别人那里继承来的，或者是从雇主那里得到的，但人们的确经常在当地公司的股票上过度投资。他们可能开车时常常经过这些公司的总部、有邻居就在这些公司上班，他们因此相信这样的投资很牢靠。

他们认为这样能降低风险、优化收益，因为老话不是说了嘛：投资你了解的东西。不过，在某只股票上集中投资实际上反而会加大风险，就像持有家得宝、星巴克(Starbucks Corp.)、Washington Mutual Inc.的人遭遇的那样。幸运的是，现在是实现投资多元化的好时机。股价在跌、联邦长期资本利得税税率目前或许正处于长期以来的最低水平。

T. Rowe Price Group驻巴尔的摩理财顾问斯图亚特•里特(Stuart Ritter)说，这是一种很普遍的现象。我们都以为对自己熟悉的东西了解的更多。

加州大学尔湾分校(University of California, Irvine)Paul Merage商学院金融学教授大卫•赫希莱菲(David Hirshleifer)说，人们对熟悉的东西很自然地会比较喜欢。

他说，我们把习惯的东西当作朋友一样，因此，投资者会喜欢买本地股票，向本地慈善机构捐款。基于同样原因，投资者更倾向于买本国股票，对外国投资产品不愿涉足。

得克萨斯大学奥斯汀分校(University of Texas at Austin)McCombs商学院金融学教授Bing Han说，相反，对不了解的公司投资者多有怀疑。

“不熟悉的东西你对它们的回报率会非常悲观，”他说，“因为你不了解，你就觉得风险比较大”。

由于这个原因，投资者一而再、再而三地购买本地公司的股票，即使从未了解过这些公司的赢利情况。但可笑的是，这些他们觉得安全的东西却给他们带来了相反效果。在某一只股票上的投资超过整个投资组合的10%就比较危险了。

花旗集团(Citigroup Inc.)旗下Tailored Portfolio Group董事总经理、全球负责人埃德•芒绍尔(Ed Munshower)说，一般来说，人们集中持有某只股票是因为他们认为，某些股票长期而言会有出色表现。

但花旗集团今年早些时候发表的报告显示，为分散个股风险，一个投资组合中应该持有25-30种股票。它发现，在过去20年中，在任何一个连续3年考察期，每10只股票中只有1只股票能持续好于标普500指数的表现。此外，任一年份该指数都有三分之一的股票表现较大盘低15%甚至更多。

芒绍尔说，对于拥有高额和超高额资产的客户而言，在投资组合中集中持有某一只股票并不罕见。“很难让集中持有某个头寸的人卖掉它，”他说。有时，这里有感情上的因素，“但现在正是将集中的头寸分散出去的绝佳时机”。

这是因为，现在市场正在下跌，而且，不论下一届谁当总统，目前15%的资本利得税税率都很有可能上调。

对于应以什么速度分散投资，理财顾问有不同看法。一些人认为应立刻卖出，其他人则倾向于在几个月内分步转换。

投资顾问公司Mainstay Capital Management首席执行长大卫•库德拉(David Kudla)说，我们有些客户在某只股票上的持仓占其投资组合的20%、30%、40%、50%甚至60%，“我们会费很大力气说服他们相信，需要在一段时期内把投资分散开。”有时投资者是在那家公司工作，有时他们是从别人那里继承了这些股票，但普遍情况是“他们认识在那家公司工作的人”。

在密歇根，这意味着一个不幸的结果：很多人都持有太多的汽车三巨头的股票，这些股票现在可是惨得很哪。

Jilian Mincer