Comparing this quarter to the same quarter last year properly

4 days ago
3 min read

Updated: 2 days ago

Introduction

Almost every small business comparison is against the previous period. This quarter against last quarter, this month against last month. It is the easiest comparison to make and it is wrong for any business with a season, which is most of them.

If your quiet period is January to March and your busy period is May to August, then a rise from the first quarter to the second tells you the calendar moved. It contains no information about whether anything you did worked. The same comparison in reverse produces a panic every autumn about a decline that happens every year.

The year-on-year comparison removes that, at the cost of needing a year of data and a little more patience. It is the comparison worth building the habit around.

1. Comparing this quarter to the same quarter last year removes the season

The core reason.

Both periods sit at the same point in the annual cycle, so what remains is change rather than calendar. This is the whole argument for the method. Everything else is detail.

2. It needs the definitions to have held

The precondition.

If you started counting enquiries differently in June, the two quarters are not measuring the same thing. Check that before drawing conclusions. This is the commonest reason a year-on-year comparison misleads.

3. Compare counts and rates separately

The two views.

Enquiry volume year on year tells you about demand and marketing; conversion rate year on year tells you about the process. Mixing them into one revenue figure hides which moved. Put them on adjacent rows.

4. Note what was different about last year

The context requirement.

A price change, a closure, a large one-off contract or a member of staff leaving all distort the base period. Write the note beside the number. Without it, next year's comparison inherits an unexplained anomaly.

5. Use the same length of period

The obvious trap.

Thirteen weeks against fourteen, or a quarter containing an extra bank holiday, produces a difference that is purely calendar. Count working days if the effect is material. For most businesses it is small but worth knowing.

6. Two years is much better than one

The stability point.

A single prior year might itself have been unusual, and you cannot tell from one comparison. Three points show a direction. This is the main reason to keep records past their apparent usefulness.

7. Keep the quarterly series visible

The presentation.

A simple row of quarterly figures going back two or three years makes the seasonal shape obvious to anyone looking at it. Charts help but are not necessary. The row of numbers is usually enough.

8. Do not abandon the shorter view entirely

The balance.

Year-on-year is slow, and a serious problem should not wait six months to be noticed. Watch a rolling three-month figure for early signals and use the annual comparison for judgement. The two answer different questions.

9. Decide the comparison before the results arrive

The discipline.

Choosing which comparison to present after seeing the numbers is how reporting becomes advocacy. Fix the method once. It will be uncomfortable in some quarters, which is the point.

Be careful about a business that has genuinely changed shape. If you moved into a different service or a different type of customer, the same quarter last year describes a different company, and the comparison needs a note saying so rather than a conclusion.

Conclusion

Make the year-on-year comparison your default and keep the previous-quarter view for early warning.

Confirm your counting definitions held across both periods, compare volumes and conversion rates on separate rows, record what was unusual about the base period, use equal-length periods, extend to two or three years as soon as you have them, keep the quarterly series visible so the seasonal shape is obvious, and fix the method before the numbers arrive rather than after.