Platinum-iridium kilogram losing 60 µg/century

What about mass? Mass is still defined by a platinum-iridium weight locked in a vault in Sèvres, France, and it is the international standard for mass. Anyone who wants to measure it has to go to Sèvres, France. It's only taken out of the vault about once every ten years, and so far as they can tell statistically, it's losing 60 micrograms per century. So if you can delay delivery on some product that you sell by the pound, you can make a little extra money.