Boundaries should always have constant slopes. The best example I'm familiar with is the benefits that kick in for a US employee who works full time. This res

Boundaries should always have constant slopes. The best example I'm familiar with is the benefits that kick in for a US employee who works full time. This results in companies doing a number of actions to get their workers to work near enough to full time without crossing that line. 11 people working 36.5 is much cheaper than 10 working 40. If the law instead was sloped, offering a partial benefit equal to hours/40, this wouldn't happen. (To avoid creating an incentive for mass overtime, the law would allow for over 100% benefits.)