Moore's Law for razor blades:

...Twin blades seemed plausible. Three were a bit unlikely. Four, ridiculous. And five seems beyond the pale. Few people, though, seem willing to bet that Gillette's five-bladed Fusion is the end of the road for razor-blade escalation. More blades may seem impossible for the moment -- though strictly speaking the Fusion has six, because it has a single blade on its flip-side for tricky areas -- but anyone of a gambling persuasion might want to examine the relationship between how many blades a razor has, and the date each new design was introduced.

This relationship (see chart) suggests shavers are going to get more blades whether they need them or not. However, just like Moore's law -- the observation that computer chips double in power every 18 months or so -- it seems that technology as well as marketing determines the rate at which new blades are introduced...

...So what does the future hold? With only five data-points, it is hard to be sure exactly which mathematical curve is being followed. If it is what is known as a power law, then the 14-bladed razor should arrive in 2100.

Of course this story from The Onion anticipated real-world developments by over 18 months.