RE: Per Quarter?

It's not.

'Quarter' is fine - but since Q1, etc, refer in statistical analyses to quartiles, I'd favour '2009 Sales Analysis by Quartile'.

Q1, as referred to here, etc, are quarters, not quartiles. Quartiles are quite different. Quartiles apply to sorted data sets, not temporal data sets. If we also write quartiles as Q1, etc, this is because of a dire shortage of letters in the alphabet for all the things we wish to have symbols for. The first quartile is the lowest 25% in relation to some attribute, not the first three months. See http://en.wikipedia.org/wiki/Quartile For example, my daughter is in the fourth quartile for height because she is taller than (at least) 75% of other girls of her age.

Of course, there are economic quartiles (based on the financial year).

there are economic quartiles (based on the financial year).

No, those aren't quartiles either (writes a professional economist). They are the quarters of the financial year.

"Sales per quarter" or "sales analysis by quarter" is what I'd expect to see in business English

I've never heard a three-month period referred to as a "quartile", but I'm sure I will one day

"No, those aren't quartiles either (writes a professional economist). They are the quarters of the financial year."

Either trax and ivie are insane (and I know that one of them is not) or there is something lost in translation (an aside: an overrated film).

Tony, I think you misunderstand nutrax and iviehoff.

Quartiles: say you look at a set of data, for example the height of a group of people. Dividing the data into quartiles involves ordering the data by height and finding out where the cutoff point is for the bottom 1/4 of the data, the bottom half and the top 1/4. John is in the lowest quartile if he is shorter than the shortest person in the 25th percentile. Everyone from the 0 to the 24th percentile is in the bottom quartile, the 25th-49th percentile are in the second quartile, 50-74th percentile are in the third quartile, and 75-99 is the top quartile.

So when you talk about "economic quartiles (based on the financial year)," you could be right that these are quartiles if what you're talking about is a set of economic data that happens to have been measured over one financial year, but it sounds like what you're referring to is what are commonly called quarters, not quartiles. (The periods January-March, April-June, etc.)