Attention shoppers, today's special: Kroger shares, 40% off

Grocers got a preview of what's to come after Amazon's purchase of Whole Foods this week as the company dropped prices at its newly acquired grocery stores. Shares of Kroger were down 37% year-to-date, and have fallen about 11.4% in August. About 28% of its retirement plan assets are in company stock. Target and Wal-Mart, both of which run more diversified businesses, were down 4% and 2.5% in August, respectively. Target holds about 23% of retirement plan assets in its stock, while Wal-Mart's plan has about 12%.

Short-interest ratios spiked in their mid-August readings. The number represents the average number of days a short seller should expect to repurchase their shares; five is typically viewed as the threshold of bearish investor sentiment.

Note: The percentage of shares held by pension plans does not include exposure through investment managers.