Board-Ansicht
Mix-Ansicht- Mark Hulbert: August is getting a bum rap - Amanito, 25.08.2005, 10:16
- Fakt ist, daß Amerika ab Labour Day wieder in voller Breite da ist.... (o.Text) - TESLA, 25.08.2005, 12:35
Mark Hulbert: August is getting a bum rap
-->An exception to this general rule would exist if some plausible explanation existed for why August should be such a good month for stocks in the early part of the last century but a bad one ever since. But I am aware of no such explanation.
Kommentar: mE hat er nicht recht, weil wir nur selten eine sog. rationale Erklärung haben für das Marktverhalten, September z.B. war anscheinend immer der schwächste Monat über einige Subperioden und trotzdem haben wir überhaupt keine gute Erklärung dafür (zumindestens habe ich noch nie eine gesehen, die mehr als eine Verlegenheitslösung ist). Im Zweifel haben fast immer die (auch unerklärten) empirischen Muster Vorrang, nicht die sog. rationalen Erklärungen oder deren Fehlen, und N=54 (1951-2004) groß genug ist, um daraus fundierte Schlüsse zu ziehen, an der Börse ist man oft gezwungen, mit kleinem N zu arbeiten.
A surprisingly large number of the newsletters I monitor are blaming stock market weakness this month on August's supposed tendency to be a bad month for equities.
I must admit it's a convenient theory. For example, it allows brokers to explain to their clients why they shouldn't blame them for their portfolios not performing very well during August.
But there's one problem with this theory: It's wrong.
Since 1896, when the ($INDU: news, chart, profile) Dow Jones Industrials Average was created, August on average has been one of the best performers. It's only in recent decades that the market has found it rough going during August.
To be sure, the investment community has never distinguished itself for having a long-term memory. But in this instance, short-sightedness has led advisers into believing that the recent past is representative of the longer-term record.
It's not.
The accompanying table shows how August stacks up against all other months, as judged by average changes in the DJIA:
Period August's average change August's rank relative to other months
1896-2004 1.28% 3
1896-1950 2.68% 1
1951-2004 -0.12% 11
1990-2004 -1.66% 11
Notice that the historical data paint a far different picture depending on the time period chosen. In general, August's rank is higher to the extent that the early decades of the last century are included, and lower to the extent they are excluded.
What conclusion can we draw from this? From a statistical point of view, not a lot. Whenever polar opposite pictures get painted by different time periods, it sends a big warning flag against drawing firm conclusions.
An exception to this general rule would exist if some plausible explanation existed for why August should be such a good month for stocks in the early part of the last century but a bad one ever since. But I am aware of no such explanation.
There's a deeper lesson in all of this, having to do with the huge amount of statistical noise in the stock market data. Behavioral researchers have shown that our psyches are unable to truly contemplate that randomness; we find patterns even in data that have no pattern.
This means that many of the stories that advisers concoct to explain what's going on are really nothing more than tall tales.
My bet is that advisers' story about August is one of them.
<ul> ~ http://www.marketwatch.com/news/story.asp?guid={5F65001F-FBCF-47C9-A279-931137A8</ul>
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