Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Expect a flat start to the stock market today, as the Dow Jones Industrial Average (^DJI -0.04%) lost an insignificant 15 points in premarket trading this morning. Global stocks were mostly higher in overnight trading, led by a 1.23% gain in Japan's Nikkei index.

The ADP national employment report today showed a gain of 175,000 nonfarm private-sector jobs in the U.S. last month, on par with what economists expected but below the 227,000 jobs added in December. The official jobs report from the U.S. Bureau of Labor Statistics, which the ADP report aims to track, is due out on Friday morning.

Meanwhile, news is breaking this morning on several stocks that could see heavy trading in today's session, including CVS Caremark (CVS -0.90%), Merck (MRK 0.36%), and Time Warner (TWX).

CVS Caremark announced today that it will stop the sale of cigarettes and other tobacco products across its 7,600 stores and pharmacies nationwide by October of this year. Citing the fact that smoking is the leading cause of premature disease and death, the company said that selling tobacco products is "inconsistent with our purpose" of supporting the health of patients and customers. CVS also plans to lead a national program aimed at helping smokers quit. The company expects to lose approximately $2 billion in annual revenue from tobacco sales, which will hurt 2014's profit by between $0.06 and $0.09 a share. CVS' stock is down 1.7% in premarket trading.

Merck today posted fourth-quarter earnings results that were in line with Wall Street's estimates. Sales fell by 4%, to $11.3 billion, and adjusted profit rose by 6% to reach $0.88 a share. The pharmaceutical giant's drug portfolio notched flat sales after accounting for foreign currency changes, as strength in a number of products offset the decline of the asthma drug Singulair, which fell 69% last year after losing patent protection. Merck also provided its outlook for 2014, which called for sales and adjusted profits to both fall slightly, to roughly $43 billion and $3.43 a share, respectively. Merck's stock is up 1.6% in premarket trading.

Finally, Time Warner this morning announced that fourth-quarter sales rose by 6% to $8.6 billion, above analysts' expectations for $8.4 billion. Earnings ticked higher by 1%, to reach $1.17 a share. The company's Warner Bros. division got a boost from the popular theatrical releases of Gravity and The Hobbit: The Desolation of Smaug in the quarter. The HBO business also kicked in higher revenue as subscription rates improved. Time Warner's stock is up 1.4% in premarket trading.