The stock market continues to weaken, as evidenced by these ETF charts. If you zero in on a sector you wish to short, I would bear in mind that ETFs are comprised of market leaders. I would look for names "outside" of the ETF components; consider them leaders and you want the weaklings to short.
The reasons for weakness are numerous.
Consider the election weight (a Trump win would weigh on equities but Clinton weighs on pharma pricing). Then there are flat-to-dropping sales. Of course the USD movement (up will weigh on commodities and large caps with overseas exposure). Then there's those who feel we are already at or above maximum value and they're not buying here. They're hedged, short some and long financials ahead of the Fed rate hike. Then there's that Fed hike itself. High dividend is flushing down the toilet (SDY) in September. Overseas weakness with China not helping boost confidence for demand. And we also have more failure at the OPEC talks with no offer from o