All broadband services are offered with the understanding that service is subject to a contention ratio. In effect it means your service whether it is 0.5 mb, 1.0 mb or 2.0 mb is "shared" with others.

The normal contention ratio for domestic services is 1:50. So in theory, at the busiest times, your service could be the equivalent of 2.0mb/50= 40k/sec!

In reality you'd be very unlikely to be in that position. Also bear in mind that the site from which you are downloading will itself have capacity limits.