(New York)

If you are looking for the canary in the coal mine for the current market turbulence, look no further than a handful of stocks that should show investors where things are headed. Especially for the Dow. The index’s gains this year have largely come from three stocks: Apple, Boeing, and UnitedHealth Group. 16 stocks in the 30-stock index have losses this year, but because of the quirky way the Dow is calculated, some smaller market capitalization companies have much more weight than larger ones (weighting is done by share price not market cap). Accordingly, this trio has outsized importance to the index, and if they fall, the Dow is likely to get badly hurt.

FINSUM: The Dow is quite funky, but this story points out just how vulnerable the whole index looks right now.