Daniel Berlinger has noticed that Mac software shops are starting to move to OS X-only development. This makes sense, for two reasons. First, most people who pay for software have new computers. So while OS X may only have a small fraction of the installed base, it has the majority of the population of people who are opening their wallets. Second, if OS X isn’t successful, the Mac is over. It’s not like System 9 is getting any more popular.

Then again, there are very few conditions under which it is actually the right business decision to develop software for the Macintosh. Developing for the Mac is not a whole lot different than creating a web site that only works on Netscape. (Given the market share of Macs (about 3.5%) and the market share of Netscape (about 3.4%), that is not a silly comparison.)

Robb Beal wrote: “Try this test. Go to a venture firm, angel, or big company with a Mac OS X product/concept/prototype. Do they consider the fact that it’s a Mac application a net plus? (No.)” Well duh. Your product would have to appeal to 25 times more Mac users [as a percentage] than Windows users just to break even. In other words, if your Windows product appeals to 1 in 100 Windows users, you have to appeal to 25 in 100 Mac users to make the same amount of money.

Now, you may want to make an emotional appeal to developing for the Mac. That’s fine. If you like Macs and you’re doing it for fun, more power to ya.

But as long as we’re talking investment, you have to tell me why you’re going to get 25 times as many users. Maybe there’s less competition in your category on the Mac; maybe you’re in a niche like graphics where it seems like Macs dominate (they don’t, it just seems that way because the elite graphics people in big American cities use Macs); maybe your product can’t sell to mixed environments unless it runs everywhere. But if you want to make an investment in Mac software be prepared to demonstrate how you’re going to overcome that magic 25 multiplier.