Hi @PhilT, you raise an important issue. Unfortunately we don’t always know when a product has been reformulated, which is why we re-test every year (they’re called fast moving consumer goods for a reason).
Reformulation aside, some of the variance can also be explained by inconsistencies in the manufacturing process or, though we try and buy ‘fresh’ detergents for the test, by the age of the product - active ingredients can degrade over time.
With regard to products coming and going from the results, as I mentioned we start from scratch each year. While our aim is to test the most popular products that are readily available, we are limited by the number of products we can test. Some years we just can’t include certain products due to the test capacity.
You’re certainly right in that a detergent that performs well year after year and test after test is a safe choice though.
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