Alts are flat out getting pummeled. Of course, there isn't any kind of agreed-upon index, but based on some concepts I've been messing around with, if you subtract out BTC and LTC, the rest of the alt market is down 20-30% over the last week.
Right now, TOTAL crypto market cap is 7.905 billion. BTC and LTC make up more than $7.6 billion. EVERYTHING else combined...hundreds of alts, don't combine to make $300mm in cap.
That is partly due to 3 big IPOs running atm. Ethereum, StorJ and Syscoin.
There are some people claiming it's because of those IPOs, but wouldn't that just dry out the supply? It would only crash the market if those coins got sold by the people behind those IPOs, and the Ethereum coins haven't moved so far, have they?
Many people have all their BTC locked up in alts, so to participate in an IPO they sell their coins to get BTC. Thus creating downward pressure.