NEW YORK — Deal makers from New York to London had a busy first half of the year, and mega-mergers drove the frenzy.

Companies around the world announced mergers and acquisitions worth $2.3 trillion, according to figures from data provider Dealogic, the second-best half-year total on record and the highest amount since 2007, when $2.6 trillion of deals were announced.

The tie-ups included 31 deals worth $10 billion or more, accounting for 39 percent of the total. That’s the largest share since the second-half of 1999, at the peak of the dot-com bubble.

The rush to merge has been driven by low borrowing costs and steady but unspectacular growth in the U.S. economy, which have sent CEOs hunting for new ways to expand sales and boost earnings. Companies from ketchup maker Heinz to oil producer Shell have joined the M&A throng this year.

“The mega-mergers, the big deals, have come back into favor,” says Neil Dhar, U.S. capital markets leader at professional services firm PwC.