Quote from newwurldmn:
The charts don't matter. It's the calculation method that does. VXX and VXZ are the closest to the continious VIX contract.
As you are not inclined to do the research yourself here is the Yahoo! description of the VXX:
The investment seeks to replicate, net of expenses, the S&P 500 VIX Short-Term Futures Total Return Index. The index offers exposure to a daily rolling long position in the first and second month VIX futures contracts and reflects the implied volatility of the S&P 500 index at various points along the volatility forward curve. The index futures roll continuously throughout each month from the first month VIX futures contract into the second month VIX futures contract.
The product doesn't approximate the VIX because it's not intending to. It's approximating the futures which calibrate to a different "volatility" than the VIX.
The VIX is essentially a basket of front 2 month listed SPX options and every day you sell about 1/20th of the front month and buy 1/20th of the second month. Unless you are willing to trade 1000 strikes everyday you CANNOT (I REPEAT CANNOT) replicate the VIX. Everything else is an approximation.
The futures calibrate to different months (like the 3 and 4 month) or such.
Based on the questions you have asked in the options forum, you probably don't understand how implied volatility works. If that information was options trading 201, then the VIX is options trading 501 (the graduate level course).
If you are interested in more, read the white paper on the VIX on the CBOE website.