Mavis and Bob share the housework, and Bob's cousin Enzo, who lives with them, also chips in. Mavis does 80 per cent of it, Bob 15 per cent, and Enzo does the remaining 5 per cent. Mavis, Bob and Enzo all have full-time jobs, and (just to keep this simple) each of them works approximately the same hours and as hard as the other two; there are no further differential facts about their respective circumstances affecting how much housework each could, in principle, do. As things are, the house is kept in reasonably good order, but for the whole of the coming week more housework effort is going to be required of them because there are going to be family visitors, and Mavis, Bob and Enzo agree that they'd like to keep things up to a better standard than usual during that time.
Should the extra input that will be required be divided equally between Mavis, Bob and Enzo?
It seems plausible to suggest that in order to answer this question fairly, you'd need to look at the basic structure of how the relevant work is already shared out, and not treat the extra effort now needed as a one-off burden to be distributed equitably. It might be thought, for example, that Enzo should take it on, or Enzo and Bob between them.
There's a piece here posing the question, 'Could you accept a pay cut or a low pay rise for the greater good? And should you?' It's in reference to public sector workers. But save for a single sentence referring to workers in the private sector 'getting pay rises markedly above inflation', there's no comparative dimension at all and no consideration of the basic structure of effort and reward across British society. It's as if that was just part of an unalterable natural order. Karl Marx had a word for this kind of thinking.