Difference of methodology that is all not. I use both as a...

Difference of methodology that is all not. I use both as a reference. Each has benefits and often simply a personal preference of choice of use or comfort. I sometimes also review ETFs like BBC as well to effectively benchmark a benchmark. For me it depends on the stock and the timeframe. As an index ICEBIO perhaps a more pure multi-exchange Bio index whereas NBI is both Bio and Pharma inclusive and hence perhaps the correlation you have witnessed despite limited in range of coverage to Nasdaq listings. Both also heavily large cap skewed. Whether long or short this is where I like to look for divergence between the sub index of choice and a larger index like the S&P 500 with an asset base upwards of 400X the Bio Pharma FUM pool as a secondary indicator. And if divergence exists I then take note and at least attempt to consider why. And if your stock of choice is moving against the tide I definitely pause to take a second look to consider why. Example 30 day % movement charts below. Here we clearly see recent accelerated NBI growth compared to S&P500 with trajectory for both in sync. Note though the CU6 trend against against both the S&P500 macro and the NBI micro trend. Short or longer term problem? An issue perhaps only for Traders and nothing worthy of concern for FA investors? Or perhaps simply an indication of multiple scenarios as discussed. Something to ponder ! Again !