For Portfolios, Simple May Be Best
When it comes to picking stocks, investors are better off buying a few companies they know very well than investing in many stocks they know little about.
New research finds that stock trades made by households holding only one or two stocks outperformed those with more diversified portfolios, according to finance professors at the University of Michigan and the University of Illinois at Urbana-Champaign.
Wealthier investors -- those with brokerage accounts of $100,000 or more -- who held concentrated portfolios also outperformed comparable households with diversified accounts by at least four percentage points a year. In fact, wealthy households that invested in many stocks underperformed the markets by about 1% a year.
That advantage appears to stem from having access to information, either through strong social or professional networks, that makes investors with concentrated portfolios better stock pickers, researchers said in a paper released last month. Although households with relatively large portfolios can afford to buy more stocks, they appear to concentrate their holdings because they have better information about those companies.
Simply reducing the number of stocks in one's portfolio won't automatically improve returns if investors don't have good information, says Clemens Sialm , assistant professor of finance at Michigan's Stephen M. Ross School of Business and one of the study's co-authors. The study analyzed 1,156,000 stock trades that individual investors made through a discount broker from 1991 to 1996.
The study also found that the outperformance of households with concentrated portfolios is particularly strong if they hold "local" stocks -- defined as companies located within a 50-mile radius of their residences. That is because investors who live near the company they are investing in are likely to know more about whether that business is worth investing in, Mr. Sialm suggests.
Meanwhile, investors with concentrated portfolios also outperform the broader market if they hold small stocks or companies not included in the Standard & Poor's 500-stock index, since those companies aren't likely to be well known or as widely followed.
On average, investors who held one or two stocks outperformed those who held three or more by about one percentage point during the year following a stock purchase. For households with portfolios of $25,000 to $100,000, the difference in returns for concentrated versus diversified investors is three percentage points. Households with stock portfolios valued at less than $25,000 didn't perform materially better.
The tradeoff, of course, is that holding fewer stocks increases the risk of those portfolios. The study did not look at the other investments the households may have had, such as retirement accounts or pension plans, so their brokerage accounts may comprise only a small portion of their total wealth.
简单的组合或许就是最好的
在挑选股票的时候，投资者最好是买几只非常熟悉的股票，而不是买很多根本不了解的股票。
密歇根大学(University of Michigan)和伊利诺大学Urbana-Champaign分校(University of Illinois at Urbana-Champaign)最新的研究显示，只投资一、两只股票的家庭的投资回报情况要好于投资更加分散的家庭。
在富裕一点的投资者当中，即帐户资金至少10万美元的投资者，投资比较集中的人比那些投资很分散的人每年回报率至少高出4%。其实，投资很多股票的富裕投资者的回报还比大盘的年回报率低大约1%。
减少的投资品种的好处似乎是来自于投资者能获得大量信息，通过强大的社会关系网络或职业关系网络挑选到更好的股票，这份于上个月发表的报告显示。虽然投资额大的人有能力购买更多股票，他们似乎更喜欢只投资某些股票，因为他们对这些公司的了解比较深。
如果没有高质量的信息，即便是减少投资不同股票的数量也不一定就能提高回报率，密歇根大学斯蒂芬?罗斯(Stephen M. Ross)商学院金融学副教授克莱蒙思?塞姆(Clemens Sialm)说。他也是这项研究报告的撰稿人之一。这份报告分析了从1991年至1996年间个人投资者通过一个折扣经纪商所进行的1,156,000笔股票买卖交易。
这项研究还发现，那些持有“本地”公司股票的集中型投资家庭的回报率尤其高。“本地”公司是指那些公司处于投资者居住地方圆50英里之内。塞姆说，这是由于住处与所投资公司距离很近的投资者更有可能知道这家公司是否值得投资。
与此同时，如果集中型投资者所持有的股票是小型股或者是非标准普尔500指数成份股，则回报也会更高。因为那些公司大多不太著名，或者是没有被广泛追踪。
一般来说，在购买股票一年后，只持有一种或两种股票的投资者比持有三种或更多股票的投资者的回报率高大约一个百分点。投资额在2.5万美元至10万美元的家庭，集中型投资和分散型投资的收益率差别达到三个百分点。这种差别在投资额少于2.5万美元的家庭间不太明显。
当然，这也是正常的，投资的股票种类少，投资组合的风险就比较高。这项研究并没有考察这些家庭可能持有的其他投资，比如退休帐户或养老金计划等，因此，他们在经纪公司的帐户可能只是他们财产的一部分。
