Can “prior” or “previous” be used to describe the same month of last year?

Question

If I want to show the comparison between rate in 2010 Jan and 2009 Jan, which of the following should I use?

1. Comparison of rate between 2010 Jan and its prior month.
2. Comparison of rate between 2010 Jan and its previous month.

Answer 1

In my opinion, neither previous nor prior work in this context for what you want to express, because both expressions imply December 2009.

Also, 'between' is a bit vague, because while the context implies you are comparing the rates of the two months, 'between' carries the idea of comparing the rates for the whole period between those two months.

Why not simply 'Comparison of rates: Jan 2010 and Jan 2009'? It is not especially clever, but it is shorter than the two phrases you propose.

Answer 2

Neither "previous" nor "prior" are correct here, because they would refer to December 2009.

If you want to use a business analysis buzzword, you could use "year over year", as in

Year-over-year comparison of rates for January

If you are addressing normal people, however, I'd suggest simply

Comparison of rates between January 2010 and January 2009

Answer 3

The Oxford Corpus of English lists several example sentences for prior:

She visited me on the day prior to her death.

Mrs Scott had to spend two weeks in hospital, including a week prior to the Caesarian birth.

For previous:

The month previous to publication . . .

The starting grids are based on a reversal of the finishing order of the previous race.

Both prior and previous have similar definitions: 'existing or occurring before in time or order' and 'existing or coming before in time, order, or importance' respectively.

From these two points (examples of usage in English and dictionary definition), I can see no evidence that either word is more or less appropriate in your context. However, I would say the following sound better:

• Comparison of rate between January 2010 and the prior month.
• Comparison of rate between January 2010 and the previous month.

That is, I would use the rather than its, although your sentences are grammatical.

EDIT: Now that I understand that the OP was talking about comparing January 2009 and January 2010, I offer these suggestions:

• Comparing the rates of January 2010 and the prior January.
• Comparing the rates of January 2010 and the previous January.

I also agree that it would be easier, and perhaps better, just to say 'Comparing the rates of January 2009 and January 2010.*

Answer 4

In general for comparing corresponding periods across years you use the expression year on year

Answer 5

Neither prior nor previous are words necessary to convey the meaning of the statement. The clearest way, so that no one misunderstands the question, is to delineate it completely:

Comparison of rates between Jan 2009 and Jan 2010.

This "statement" implies that there is a list to follow with the said comparisons indicated. It is not meant to convey all of the actual comparisons. It seems to be more of a heading.