Compare

This site does not rank or star-rate ingredients and procedures. The comparison tables are no different.

The row order is the layer and the seed order, and being higher up does not mean better. Where several items share a grade, adding any second sort key would make that key another ranking, so there is none.

And every row carries the title of the finding that grade hangs on. Without it, the row reads as 'this ingredient's score'. It is the same reason we do not average when a page has several findings — an average is a number nobody measured.

Which finding goes in the table is a rule too. If the comparison names a question, that finding (as with the three measured against hydroquinone in the brightening set); if it names none, the highest-graded finding. Entries marked as ingredient data — facts from an ingredient list or a regulatory document — are not efficacy claims, so they are never the representative.

Putting two ingredients' 'percent improvement' side by side usually says nothing at all. Four things have to match first.

• the endpoint — a blinded rater's score, an instrument reading and a biopsy count different things. Retinol rests on rater scores, retinaldehyde on instrument readings
• the comparator — vehicle, moisturiser and no treatment are different questions. A 50% against no treatment can be a weaker result than a 15% against vehicle
• the duration — four weeks and 24 weeks are different trials
• the funding — evidence that is entirely industry-funded cannot be read at the same weight as evidence that is not

So the use of these tables is not in comparing the numbers. It is in making it visible at a glance that those four do not line up.