The other problem is with overhead 2 half time employees != 1 full time employee. There is the extra equipment cost, benefits (perhaps), management overhead etc

The other problem is with overhead 2 half time employees != 1 full time employee. There is the extra equipment cost, benefits (perhaps), management overhead etc. e.g. If I replace a team of 7 full time engineers with 14 half time engineers, do I keep 1 manager? That seems like a very large team for 1 person to handle, so now maybe I need another manager too. From a purely economic perspective hiring half time engineers at half the comp just doesn't seem to make sense. You can argue that half time engineers are more than half as productive as a full time engineer because as others have said full time engineers don't work a full 8 hours anyways. While theoretically that's true, as I originally posted, that's not what I've seen. Based on my anecdotal experience, half time engineers are less than half as productive as a full time engineer. So from both a productivity and economic perspective, it hasn't made sense.