putting cash under your mattress has security costs. For < 1k euro, probably not worth calculating. But for > 1M euro, there is a real security cost to keepin

putting cash under your mattress has security costs. For < 1k euro, probably not worth calculating. But for > 1M euro, there is a real security cost to keeping that amount of cash safe for 30 years. I may be totally wrong, but I think the floor on negative yields is going to be the security costs of keeping cash for that timeframe.