U.S. stocks are hardly budging Tuesday as investors wait for British voters to decide the fate of that nation’s membership in the European Union. Phone and energy companies are rising and drug companies are falling. Stocks posted big gains a day ago.

KEEPING SCORE: The Dow Jones industrial average picked up 21 points, or 0.1 percent, to 17,826 as of 12:08 p.m. Tuesday on Wall Street. The Standard & Poor’s 500 index rose 4 points, or 0.2 percent, to 2,087. The Nasdaq composite lost 1 point to 4,836.

ALL EYES ON BRITAIN: Opinion polls and betting markets indicate that Britons are more likely to vote to remain in the European Union in a referendum Thursday. Uncertainty about the outcome has weighed on global markets, and polls suggest the result will be close.

YELLEN TESTIMONY: Federal Reserve Chair Janet Yellen spoke to the Senate Tuesday and said the U.S. economy faces a number of uncertainties that require the Fed to proceed cautiously in raising interest rates. Those problems include a slowdown in job growth in April and May. Yellen said the Fed will watch carefully to see if that slowdown is temporary or a sign of a bigger problem.

CHECK YOUR MESSAGES: AT&T added 30 cents to $41.09 and Verizon gained 46 cents to $54.22 as phone companies made larger gains than any other sector of the market.

FEELING ILL: Drugmaker Endo International lost $1.03, or 6.4 percent, to $15.04. It’s fallen 46 percent this month, in part because of regulatory delays for a new version of its painkiller Opana ER. Also trading lower were cancer drugmaker Celgene and cystic fibrosis drugmaker Vertex. Celgene gave up $2.19, or 2.2 percent, to $97.10 and Vertex shed $2.83, or 3.3 percent, to $83.89.

SCIENCE DEAL: American Science & Engineering, which makes X-ray inspection systems, agreed to be acquired by airport security and full-body scanner manufacturer OSI Systems Inc. OSI will pay $37 per share, or $263.9 million. American Science & Engineering’s stock jumped $4.43, or 13.7 percent, to $36.77.

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WERNER WARNING: Transportation and logistics company Werner Enterprises forecast disappointing second quarter results. It said sluggish freight market conditions are hurting rates, as are the costs associated with an increase in pay for drivers. The stock lost $2.21, or 9 percent, to $22.47. Truck leasing company Ryder System lost $1.89, or 2.8 percent, to $64.44.

TAP THE BRAKES: Used car dealership CarMax disclosed disappointing first-quarter results as its costs increased and sales fell short of Wall Street estimates. Its stock gave up $1.80, or 3.6 percent, to $48.83. Auto retailer AutoNation fell $1.44, or 2.9 percent, to $47.92 and auto supplier BorgWarner skidded $1.42, or 4.1 percent, to $33.31.

ENERGY: Benchmark U.S. crude shed $1.04, or 2.1 percent, to $48.33 per barrel in New York. Brent crude, used to price international oils, fell 93 cents, or 1.8 percent, to $49.72 a barrel in London. The price of oil rose about 7 percent over the last two days.

METALS: The price of gold dropped 1.5 percent to $1,272.70 an ounce and silver fell 1.3 percent to $17.28 an ounce.

IMPAX SLACKENS: Generic drugmaker Impax Laboratories tumbled after it agreed to pay $586 million for a group of generic drugs owned by Allergan and Teva Pharmaceutical Industries. Those companies had to sell the products because Allergan is buying Teva’s generic drugs business. Impax lost $3.58, or 11.2 percent, to $28.39.

FLYING HIGH: The parent of United Airlines traded higher as it gave investors new details on how it plans to strengthen its financial performance. United Continental Holdings aims to boost revenue and cut spending by $3.1 billion over the next few years and it also forecast a slightly smaller decline in an important revenue figure in the second quarter. Its stock added $1.45, or 3.3 percent, to $44.85.

IMPERVIOUS: Data security software company Imperva climbed $4.71, or 11.6 percent, to $45.15 after Elliott Capital, the firm run by activist investor Paul Singer, disclosed a stake.

HOME SWEET HOME: Lennar, the second-largest U.S. homebuilder, said it put up more homes at higher prices in the second quarter. It also said new orders jumped 10 percent. Its stock rose 27 cents to $46.93.

OVERSEAS: Germany’s DAX rose 0.5 percent and France’s CAC 40 advanced 0.6 percent, also adding to large gains on Monday. Britain’s FTSE 100 gained 0.4 percent. Tokyo’s Nikkei 225 rose 1.3 percent and Hong Kong’s Hang Seng added 0.7 percent while Seoul’s Kospi gained 0.1 percent.

BONDS, CURRENCIES: Bond prices stabilized after Monday’s skid. The yield on the 10-year U.S. Treasury note remained at 1.69 percent. The dollar rose to 104.58 yen from 103.96 yen. The euro fell to $1.1255 from $1.1314. The British pound edged back to $1.4665 from $1.4693 after a big jump Monday.