日前，苹果（Apple）公布最新一季财报，业绩未达到华尔街分析师预期，公司股价因此遭受重创，创下四年来单日跌幅最高记录。然而，令人好奇的是，那些分析师有没有意识到，上个财季的天数要比去年同期少了足足一周呢？

    经常看我博客的读者会知道，苹果和许多零售业公司一样，容易受到周末销售的影响。有鉴于此，苹果对一个财季的定义并不是三个月，而是13个星期。为了弥补每个财年和自然年之间一到两天的误差，苹果每隔五、六年就会额外增加一个星期（取决于这期间有多少个闰年）。因此，时间较长的财季天数要（比平均值）多出7.7%，而时间较短的财季，其天数要（比平均值）少7.1%。

    这一点看起来显而易见。然而，30多个华尔街分析师中，只有寥寥数人在苹果公布上财季财报前提到了这点。那些“自动忽略”了这个因素的分析师们自然会低估时间较长财季的营收（例如2012财年第一财季），同时，也会高估时间较短财季的营收（例如2013财年第一财季）。

    这些拿着工资去分析全球最值钱公司的专业分析师们，难道就没有意识到这个问题对他们的预测这么重要吗？

    碰巧学术界对这个问题并不陌生。去年，《会计学与经济学学报》（Journal of Accounting and Economics）发表了四位商学院教授针对这个问题的一篇论文【《14周的季度》（14-Week Quarters），约翰斯顿等著，2012年2月-4月刊】。

    四位教授研究了分析师们12年来对658家公司的预测后发现，那些没有提及某财季多出一周这一点的分析师，预测的利润比实际值高出4.2%，而预测的营收比实际值高出4.8%。（见图表5）。

    论文最后总结道，“获取这样的信息并不难，而且整合进预测也轻而易举，所以我们得出的发现着实让人惊讶。对多出的一周进行调整并非什么大费周章的事。这足以说明，这些分析师缺少的是努力，而并非能力。”

    这样的说法已经算相当客气了。不过这篇论文的引语——出自《财富》杂志（Fortune ）的一篇文章，作者是我的前同事吉姆•莱德贝特——非常尖锐。

    “显然商家们都表示，第四季度销售额上升是因为今年11月多出了一周。我想说的是，那些不看日历，在预测时不考虑这个因素的分析师，他们价值还不如一个电子表格软件。”——吉姆•莱德贝特（《财富》杂志，2007年12月18日）

    换句话说，他们不是愚蠢，而是懒惰。

    图表5见下

    译者：项航

    One of the mysteries that lingers from Apple's (AAPL) most recent quarterly report -- when the company failed to meet Wall Street's expectations and its stock suffered its worst one-day loss in four years -- was whether the analysts who set those expectations were aware that the quarter was one week shorter than the same quarter a year earlier.

    As my regular readers know, Apple, like many retail firms affected by weekend sales, defines its fiscal quarters not as three months, but as 13-week periods. To compensate for the resulting shortfall of one or two days a year, the company adds an extra week every fifth or sixth year (depending on the number of leap years in between) -- giving it 7.7% more selling days in the long quarters and 7.1% fewer in the short.

    Seems pretty straightforward. Yet of the three dozen Wall Street analysts we polled in advance of last month's earnings report, only a handful mentioned the short quarter. Those who failed to take it into account, of course, would tend to underestimate revenues in the long quarter (i.e. fiscal Q1 2012) and overestimate them in the short (Q1 2013).

    Is it possible that professional analysts paid to study the world's most valuable company were unaware of something so material to their forecasts?

    As it happens, this is a familiar issue in academic circles. Just last year the Journal of Accounting and Economics published an article on the phenomenon by four business school professors ("14-Week Quarters," Johnston et. al, JAE, Feb-Apr 2012).

    The professors studied analysts' forecasts for 658 firms with 14-week quarters and discovered that over a 12-year period the magnitude of error in the estimates of analysts who failed to mention the extra week was 4.2% higher on earnings and 4.8% on revenue. (See Table 5 below).

    "These results are quite surprising in light of the ease with which this information can be obtained and incorporated into expectations," the authors conclude. "The simplicity of making an adjustment for the extra week suggests a lack of effort rather than ability."

    That's putting it politely. The article's epigraph, taken from a Fortune article by my former colleague Jim Ledbetter, is more blunt:

    "Evidently sellers are claiming that the numbers are inflated because there was an extra reporting week in November this year. To which I say: any analyst who didn't look at the calendar and factor that into earnings projections isn't worth the price of the spreadsheet software." -- James Ledbetter (Fortune, Dec. 18, 2007)

    In other words: Not stupid, just lazy.

    Below: Table 5.