The trend is not completely nailed down....but here is how things generally pan out. When BTC is hitting All Time Highs people start flocking to it. Usually on those days, you will get just a few alt coins that grow or explode that day or those days. However, most alt coins start to suffer and revert back to their last best known support. Once BTC peaks and settles a bit, people are confident in the whole market again, and the alt coins then start to become phasic with BTC again. They are always following it, but often they are left behind to catch up. Expect a low day or two for alts, unless you are in the right places at the right times, they will likely lose a little value then start to build it back up after bitcoin decides where it's sitting this time.