A stock with a high "days to cover" value compared to its peers would be considered to have a higher level of short interest as compared to those peers. This could mean short sellers are using the stock to hedge a long bet elsewhere, or could also mean that short sellers believe the price of the stock will decline. When short sellers eventually cover their positions, by definition there must be buying activity because a share that is currently sold short must be purchased to be covered. So investors tend to keep an eye on that "days to cover" metric, because a high value could predict a sharper price increase should the company put out some unexpectedly good news — short sellers might rush to cover positions, and if the "days to cover" number is high, it is more difficult to close those positions without sending the stock higher until the higher price produces enough sellers to generate the necessary volume. Below is a three month price history chart comparing the stock performance of DUK vs. MCK: According to the ETF Finder at ETF Channel, DUK and MCK collectively make up 1.94% of the S&P 500 Low Volatility Portfolio ETF (SPLV) which is relatively unchanged on the day Friday.
According to Preferred Stock Channel, there is a series of preferred stock that is senior to DUK, which trades under the symbol FPC.PRA — more info ». At last check, DUK was down about 0.1%, while MCK was off about 0.3% on the day Friday.