A better way of looking at it might be "What proportion of software in daily use" is open-source. Sure there's a lot of proprietary software, but that's not an

A better way of looking at it might be "What proportion of software in daily use" is open-source. Sure there's a lot of proprietary software, but that's not an 'open-closed source' dichotomy where closed-source stuff can be sold for profit, it's a 'public-private' dichotomy instead. That is, Banks will keep their source-code private to prevent other banks from stealing their ideas, for example, and nothing to do with the software itself per-se.