A handful of technology companies account for a growing portion of all stock repurchases, a trend analysts say is driven in part by a need to deploy cash and please shareholders amid heightened regulatory scrutiny and market uncertainties.

During the second quarter, stock repurchases by five companies — Apple Inc., Oracle Corp., Microsoft Corp., Alphabet Inc. and Intel Corp. — comprised 43.1% of those from all S&P 500 companies with similar business models in the information technology and communications services sectors, according to an analysis by S&P Global Market Intelligence. That is up from 35% in the first quarter and 27.7% a year earlier. Given recent buyback announcements from Alphabet and others, the percentage could go even higher.

Google LLC parent Alphabet spent $6.61 billion on stock buybacks during the first half of 2019, compared to $4.22 billion during the same period a year ago. In July, the company added $25 billion to its stock buyback program, taking total new repurchase authorizations to nearly $40 billion since the start of this year and indicating buybacks should continue to mount.

Alphabet has historically been more conservative in buying back its own shares compared to its peers. During the June quarter, Apple spent $18.15 billion on share buybacks, roughly five times more than Alphabet. Oracle was the second-largest repurchaser, spending $6.30 billion, followed by Microsoft with $4.63 billion.

All four companies also rose to the top of peers for liquidity. Microsoft ranked as the most liquid, with $133.83 billion in cash, short-term investments and marketable securities as of the June quarter, followed by Alphabet with $121.06 billion and Apple with $94.61 billion.

Apple in April upped its current stock buyback program to $175 billion from $100 billion. As of June 29, about $78 billion of that amount had been paid to shareholders, the company said. Similarly, Oracle in February said its board had approved expansions of its share repurchase program collectively totaling $24 billion. About $11.8 billion remained available for stock buybacks as of Feb. 28, according to Oracle.

Alphabet has faced intensifying pressure to pay out more of its cash to investors, and Wall Street welcomed its recent commitment to purchase more stock. The company's shares jumped 9.6% the day after the tech giant announced its new buyback plan and reported better-than-expected top-line and bottom-line growth for the second quarter. Evercore ISI analyst Kevin Rippey upped his price target on the company's shares to $1,350 from $1,200 following the announcement.

Some of the initial gains have since been lost, with shares of Alphabet closing at $1,188.90 on Aug. 9, up 4.7% since July 25, the last market close before Alphabet's earnings report and buyback announcement.

Walter Price, managing director and senior portfolio manager at Allianz Global Investors, an asset management company, said Alphabet's fast-growing cash pile makes it all the more necessary to return that money to shareholders.

"I'd like to see them be much more aggressive," Price said in an interview.

Speaking on a July earnings call, Alphabet CFO Ruth Porat said the company's recent increase in its share repurchase program does not reflect a change in its financial priorities, which includes investing in the long-term growth and supporting acquisitions.

While acquisitions are generally an option for cash-heavy companies, the current regulatory environment for big technology companies such as Alphabet makes that avenue more challenging, Price noted.

The U.S. Justice Department in July confirmed that it had opened an antitrust investigation into market-leading tech companies to probe potential anticompetitive behavior in search, social media and some online retail services. As the 2020 U.S. presidential election nears, some politicians are advocating the breakup of big companies like Alphabet and Facebook Inc.

"Given the scrutiny [Alphabet] is under, big acquisitions are hard to make work," Price said.

Stock buybacks are often preferable to other investment options because they offer immediate gratification to shareholders, generally boosting the company's share price and earnings, said Howard Silverblatt, a senior index analyst at S&P Dow Jones Indices.

But repurchases also come with political risks, Silverblatt noted. Some politicians have called out companies for prioritizing short-term stock-boosting strategies over long-term business investments, which could make executives more skittish about buybacks.

"Washington definitely has an impact," Silverblatt said.

S&P Dow Jones Indices and S&P Global Market Intelligence are owned by S&P Global.