Why does your tax id only have 8 digits?

I hate to tell you but your tax ID in the United States has nine numbers, not eight. Use both hands when you do these complicated math problems. I'm just kidding. The reason for having nine digits is that so far this has been enough to designate between different taxpayers. When populations grow you need more numbers to make sure you have enough active numbers for different taxpayers. As people die, the social security numbers are recycled and reused. The same works with employer identification numbers.