What a difference a week makes

A single week can make a huge difference in the impact of an earnings announcement. How so? Well, Apple’s first quarter earnings were slammed because, in large part, their earnings were close to flat on a year-to-year basis. However, as Philip Elmer-DeWitt points out, Apple’s first quarter this fiscal year was one week shorter (12 weeks total) than last year’s first quarter (13 weeks total). The additional week last year was due to the aggregate effect of leap days that Apple aggregates into the first quarter every few years.

A direct comparison quarter-to-quarter, ignoring the addition week in the prior quarter does in fact show relatively flat profitability. However if on compares each quarter on a weekly basis (that is, total numbers for the quarter divided by the number of weeks in each quarter) on can calculate weekly year-over-year growth.

And here is a chart that does so:

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Thus, on a weekly basis, income was up nearly 8%, and the unit sales are much higher as well. For the quarter, average income of the S&P 500 was less than 4%.

Disclosure: I am long AAPL.