Starting with the SPDR S&P ETF (SPY  ) which tracks the S&P 500 we can see that it started very strong at the beginning of the week as there was a new poll that showed the UK was likely to stay in the European Union. Until that vote, traders have been unwilling to take any new risk, so the SPY has traded mostly sideways.

As for the Nasdaq 100 (QQQ  ), it has been under performing slightly. The strong market days just have not taken the QQQ along for the ride and that can be almost blamed on one individual sector. The biotech sector has continued to sell off. One of the ETF's for the Biotech sector is the (IBB  ), and traders have noted that the recent sell off has taken the IBB almost back down to the yearly low. Volume has also been very strong on down days indicating an increase in the presence of new sellers. 

So why is the IBB headed to lows? 

Well there are a few names in the sector that have been relatively weak. Stocks like Regeneron Pharmaceuticals (REGN  ) have just recently broken to new lows on above average volume. REGN lost 2% on Tuesday and was unable to get any significant bounce on Wednesday. This, along with other names in the IBB have really weighed on the Nasdaq 100. 

Moving on to Gold (GLD  ) which has pulled back from its recent highs lately, as sellers continue to take profits in the wake of a strengthening dollar (UUP  ). Overall this pullback hasn't really concerned traders that much considering that Gold is still up over 20% on the year.  

The Gold Mining Sector (GDX  ) has also seen some profit taking in the short term, but with an 80% gain on the year, traders aren't suffering yet. 

The major focus of the week continues to be the impending "Brexit" vote. We will find out their decision Thursday and traders are expecting a very volatile market. The Guggenheim Euro Trust ETF (FXE  ) is one way to participate in the Euro action.