Small changes add up faster than most people expect.
Most people meet this once and never think about it again, which is exactly why it is worth reading up on.
What it costs
The figures move about, but the direction has been the same for three years. The exceptions matter more than the rule, and there are three of them.
What to check first
The practical effect is easier to see in a single example than in a summary. Nobody is required to explain this to you, which is half the problem.
The short answer: check the date, then check the figure, then decide.