Download speeds

Call me stupid (not really) but why can't my ISP maintain download speeds=
of=20
15kb/s. It will stay between 10 and 15 for a couple of seconds (making a =
ten=20
minute download about 1 minute) and then drop back down to 5.5 (or around=
=20
there). Is there anything I can do about it?
--=20
:-)~Mike~(-: