I believe cryptocurrency industry is mature enough to have its own Dow-Jones index. Coinoindex.com will track the performance of top 20 alternative cryptocurrencies (in market capitalization) relative to Bitcoin.
The rules of index calculation:
- Top 20 altcoins by market capitalization are selected. Tracking assets ("pegged") such as CoinoUSD or NuBits are excluded. Also each of them has to have a trading volume over $1,000 during last 14 days.
- Each coin has an equal weight in the overall portfolio. I do not think that weighting by capitalization makes sense, since it can be easily pumped artificially (see Ripple Auroracoin and so on). Since the index is an analogue to Dow-Jones rather than S&P index.
- The price of the portfolio of 20 coins relative to BTC is calculated and updated every minute. The initial index value is set to be 1000. So the index value tracks the performance of 1000 BTC investment in a selection of 20 altcoins.
- Each week the portfolio is updated based on current market capitalizations. If a coin drops from top 20 list it is replaced by a new one which entered the list, the overall portfolio is rebalanced taking into account equal shares of each coin.
You can see current Coinoindex values and its composition at Coinoindex.com (this is preliminary set from two weeks ago, it will be updated after official launch)
I estimate that the altcoin market will demonstrate superior performance relative to BTC price, just as S&P and Dow-Jones indexes perform better than USD on which there are based (look at Dow Jones for example
http://www.macrotrends.net/1319/dow-jones-100-year-historical-chart). It works like investing in so called Index funds in traditional sense, you can invest in a mutual fund which tracks S&P performance, for example.
The Index is traded against BTC at Poloniex.com exchange:
https://poloniex.com/exchange#btc_indexAslo the Index Asset is traded at NXT Asset Exchange (and maybe some other exchanges afterwards), the costs for running the index will be covered by the market making spread for buy-sell orders at AE. The launch is planned in about a week. Before the launch the index will be set to 1000 again.
If anything is not so clear please ask.