But wait! This is technology. It gets better all the time, right? What gives? Let me suggest three possible reasons.

First, for high school level math classes, the TI-83 Plus and TI-84 Plus are essentially perfect. After all, the *material* hasn't changed (much), so if the calculators were good enough for us 10 or 15 years ago, they are still good enough to solve the math problems.

Second, standardized test companies only allow a certain range of calculators to be used. If they got too powerful or complex looking (seriously, the aesthetic is part of it), they could be banned, hurting their sales. Horizontally oriented calculators have been banned by the SAT, even if they have near identical functionality to vertically oriented models.

Third, and this is probably most important, teachers tend to recommend a particular calculator or set of calculators, and the more of their students using the same tool, the easier it is to teach them. That puts a drag on the change in tools because the technological system in which they are deployed militates against rapid change. TI runs a training organization (Teachers Teaching with Technology(T3)), which I'm sure helps the newer products diffuse, but there are a lot of good reasons for teachers not to follow the latest calculator trends, beyond the basic desire to reduce calculator heterogeneity. If the upgrade cycle is slow, families can hand down calculators from older kids to younger ones. Teachers can continue to use the same handouts, too, which may be pegged to the particular calculator. All these factors have made competing touch for Casio and HP, I think, too.

There have been a couple of very big changes in calculators over the past couple decades. The TI-89, which became available in 1998, let you solve equations with your calculator (just like the TI-92, but you were more likely to be able to use it on tests). It was awesome and a major upgrade from the TI-84-level calculators.

Since then, the biggest changes have come in look and interface. Recently, Texas Instruments (TI) has been playing with a touchpad instead of buttons on the newish Nspire series. Those changes have gotten a mixed reception. This year, TI unleashed the biggest interface change since the introduction of the calculators themselves: a color screen.

Here's the thing. Some technologies don't change all that quickly because we don't need them to. Much as we like to tell the story of The World Changing So Fast, most of it doesn't. Look at cars or power plants or watches or power strips or paper clips. The changes are in the details, and they come slowly. But that's ok. More change isn't necessarily better.

Perhaps the real question to ask about graphing calculator technology is why the prices haven't come down more. Memory, processing, and batteries are all a lot cheaper than they used to be but graphing calculator prices remain stubbornly high. The price of a low-end netbook is scarily close to the price of the high-end graphing calculator.