It is less complicated than it looks, once the terms are clear.
Ask around and you will get a different answer every time, so here is the short version.
Where to go from here
The exceptions matter more than the rule, and there are three of them. Most of the confusion comes from two terms that sound alike and mean different things.
Where the confusion starts
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.
You Might Also Like
Reading home insulation without a specialist
What the numbers actually say, once the headlines are set aside.
The case for rethinking weekly food shops
What to check before signing anything, and what can wait.
Reading neighbourhood libraries without a specialist
A plain look at what changed, and what it means from here.