Michael P. Regan is a Bloomberg Gadfly columnist covering equities and financial services. He has covered stocks for Bloomberg News as a columnist and editor since 2007. He previously worked for the Associated Press.

The Fourth of July holiday may have come and gone, but the summer fireworks in the stock market are just getting started as companies begin reporting second-quarter results.

If you're trying to find out which stocks will have the most dazzling moves, a good place to look is in the equity options market. At the top of the list for S&P 500 companies is the nonvoting (and somewhat controversial) Class C shares of Under Armour. Options trading in that stock is thin -- less than 200 contracts a day on average in recent weeks -- so the 15 percent expected move may be a bit exaggerated. Still, Under Armour's more heavily traded Class A shares also make the list of the top 20 expected moves from S&P 500 companies based on the implied volatility of the options on the stock.  

Under Armour, a short-seller favorite of late, is the type of company that rarely misses analysts' estimates -- it's beaten the Bloomberg consensus for adjusted earnings per share by an average of 47 percent and only trailed it once in a decade. But investors are hip to that trend, and the stock has been just as likely to fall as rise after its last 10 quarterly reports. 

Other notable consumer companies make the list, including Netflix, Chipotle, Urban Outfitters, Kohl's and Nordstrom, as well as Southwestern Energy and Chesapeake Energy: 

Follow the Vol
Options volatilites show where traders expect the biggest share-price moves after earnings reports for S&P 500 companies
Source: Bloomberg
Note: Expected dates of earnings reports are in parentheses.

Of course, these expected moves look like sparklers compared with the girandolas that could be set off from smaller companies, especial in the biotech industry, where stocks are jumpy to begin with and options could be pricing in expectations of big moves regardless of earnings.

Here's a look at the biggest expected moves of Russell 3000 companies with a share price of at least $10 and more than 500 options contracts trading daily on average over the last 20 days:  

Small Stocks, Big Moves
Biotech companies dominate the Russell 3000 Index stocks that have the highest expected share-price moves
Source: Bloomberg
Note: Expected earnings dates in parentheses when available.

Will these stocks definitely move this much? Of course not. But it does allow one to tap into the wisdom of the options-market crowds to get a sense of where traders are expecting the most excitement.  

The caveat here is these are absolute values for the expected moves -- meaning they could be either up or down. We don't necessarily know which direction. But what fun would that be? 

This column does not necessarily reflect the opinion of Bloomberg LP and its owners.

To contact the author of this story:
Michael P. Regan in New York at

To contact the editor responsible for this story:
Daniel Niemi at