Aon PLC reported fourth-quarter 2019 revenue of $2.9 billion on Friday, a 4% increase from the fourth quarter of 2018, driven by 7% organic revenue growth, as its reinsurance business soared due to strong growth in catastrophe bonds and capital markets transactions.

Four of five of Aon’s business units reported organic revenue growth of 5% or greater, in what was a “strong close to a year of significant improvement with momentum heading into 2020,” Greg Case, Aon president and CEO, said in the Friday morning earnings call.

Overall organic revenue growth was 6% in 2019, the brokerage’s “strongest level of organic growth in 16 years,” Mr. Case said on the call.

“You’ve already seen the trend of organic revenue growth consistently improve over the last six years, from 3% in 2014-2015, to 4% in 2016-2017, to 5% in 2018 and now 6% in 2019,” Mr. Case said, adding that the brokerage will deliver mid-single digit or greater organic revenue growth over the longer term.

However, total operating expenses were up 4% to $2.4 billion in the quarter, primarily due to an increase in costs related to organic revenue growth, increase in investments and higher restructuring charges, Aon said in an earnings statement.

Aon’s reported restructuring costs of $170 million in the quarter were primarily due to “workforce reductions” and other costs related to “restructuring and separation initiatives,” the brokerage said. All charges related to the restructuring program, which began two years ago, have been completed in the fourth quarter, it added.

Since the restructuring began, through the end of 2019, the broker has incurred total expenses of $1.4 billion, the statement said.

Aon has made 86 acquisitions in “priority areas” in the last five years, Mr. Case said. Its recent acquisition of digital platform CoverWallet “will serve as a building block to unlock net new opportunity in the fast-growing commercial insurance market for smaller businesses, a $200 billion global premium market with less than 5% served digitally today.”

Aon’s commercial risk solutions unit reported revenue of $1.33 billion for the fourth quarter of 2019, a 5% increase over the same period last year, including organic revenue growth of 7% driven by double-digit growth in the U.S., Aon said in the statement.

Reinsurance solutions reported revenue of $187 million, up 15% from fourth-quarter 2018, including organic revenue growth of 17% as it saw double-digit growth across every major business segment, including net new business generated globally, Aon said. There was “strong growth” in catastrophe bonds, it said.

Retirement solutions reported revenue of $494 million, down 3%, including organic revenue growth of 3%, with growth across every major business. Health solutions reported revenue of $585 million in the quarter, up 5%, and data and analytic services reported $291 million in revenue, up 7% from the 2018 quarter.

The broker reported net income for the quarter of $374.0 million, up 8% from the prior year period.

For the full year of 2019, Aon had total revenue of $11.0 billion, up 2% from 2018, the statement said. Revenue in commercial risk solutions was flat at $4.67 billion, while reinsurance solutions grew 8% to $1.69 billion. Revenue in retirement solutions was down 3% at $1.81 billion, and health solutions revenue grew 4% to $1.67 billion, while data and analytic services saw an increase of 7% to $1.18 billion.

For the full year, Aon had net income of $1.53 billion, up 35% from 2018.