Expense trend compares what you spent over the last 90 days against the 90 days before that.
Why ninety days
Month to month is too noisy in a service business — one large material order or an insurance renewal makes a quiet month look alarming. A full year is too slow to act on.
Ninety against ninety is long enough for a real change to show and short enough that you can still do something about it.
Reading it against revenue
Rising costs are not automatically a problem. Costs rising while revenue is flat is.
That is the comparison that matters and the one people skip. A business growing 30% should see costs rise; the question is whether they rose by less than 30%.
Where increases usually come from
In rough order of frequency:
Recurring charges nobody reviewed. Software, subscriptions, services. Each was justified once; the total never gets looked at. See recurring payments.
Material costs passed through late or not at all. Supplier prices moved and quoted prices did not.
Overhead added during a good stretch that stayed after the good stretch ended. This is the one that hurts, because it never felt like a decision.
Genuine growth, which is fine and should be visible in revenue.
What to do with a rise
Find which category moved before deciding anything. A 12% increase concentrated in one line is a specific problem with a specific fix. The same increase spread evenly across everything is usually inflation, and cutting is the wrong response to that — repricing is.