Solve this IP address puzzle

[Bill Haywood]

My ISP says that my IP address is issued dynamically, and therefore changes regularly. Two different ISP reps told me this months apart.

But when I check it online at http://whatismyip.com, it always reports the same address: 74.194.xx.xx.

This has been true for months. Both computers hooked up to the same router always report this address.

Any explanation why a dynamically assigned IP address always shows up the same?