Albert Einstein might have discovered the relativity of space, but it was Hong Kong developers who have made concrete the notion that the same space can have two - or more - sizes, depending on how you measure it. Unlike most developed economies, flat buyers here have for decades had to guess how much space they actually have in the home on which most of them have invested their life savings. We have saleable area and gross floor area, and no two developers agree on the same definitions on the measurements. Useable area might have been the most practical and reasonable for home buyers, but it is the one measure that is never used, unless you hire your own technician or use your own measuring tools. But when flats are new or incomplete, you have to take the developer's or real estate agent's word for it. The flashy example on display in the showroom is almost certain to be a misrepresentation. Now, finally, the government has come round to making developers state flat sizes in terms of 'saleable area' instead of 'gross floor area'. This has been long overdue. Saleable area is closest to 'carpet-floor areas'. Gross floor area can include anything the developer claims as common areas on the estate. The result has been the illusion of ever-increasing floor areas when in fact the average livable space has been shrinking. Sure, the clubhouses, car parks and other common areas get bigger, but not the flat you live in. The widespread abuse of gross floor area has done much to turn many in our society against developers. Developers are up in arms against the government's proposal, which this week starts a two-month consultation and is expected to be pushed through Legco to become law next year. They warn the sole use of saleable area will make the cost per square foot so much higher. But that's the whole point - let people realise how much they are paying for a shoebox-sized flat.