Like against like.
WHAT TO COMPARE
This month against last month This month against the same month last year This year to date against last year to date
WHY THE YEAR COMPARISON MATTERS
Seasonality makes month-to-month comparison misleading.
A December to January fall may be entirely normal.
WHAT TO BE CAREFUL WITH
Months of different lengths Different numbers of working days Holidays falling differently Part periods against whole ones
THAT LAST POINT
Comparing a partial month against a complete one is a common and misleading error.
WHAT TO NORMALISE
Per working day, where it matters.
WHAT TO ESTABLISH
Whether your business is seasonal, and how.
HOW
Plot monthly figures across two or three years.
The pattern becomes obvious.
WHAT THAT ENABLES
Knowing whether a quiet month is a problem or a season.
WHAT TO AVOID
Reacting to a normal seasonal decline.
WHAT TO RECORD
Your seasonal pattern, so it informs planning.
