The Lowy family that made its fortune through Westfield shopping centres is selling out for $32.7 billion.

Key points: Westfield shareholders will receive $10.01 in cash and shares, per share — representing a huge premium to Westfield's shares

Westfield shareholders will receive $10.01 in cash and shares, per share — representing a huge premium to Westfield's shares Westfield chairman Frank Lowy said the deal was the result of the company's restructure which began in 2014

Westfield chairman Frank Lowy said the deal was the result of the company's restructure which began in 2014 The Lowy family will retain a significant holding in the merged operation

French property giant Unibail-Rodamco is acquiring the shopping mall juggernaut.

Westfield shareholders will receive $10.01 in cash and shares, per share — representing a huge premium to Westfield's shares, which last traded at $8.50.

Unibail-Rodamco will maintain the Westfield brand and the Lowy family will "remain committed to the success of the Group" and intends "to maintain a substantial investment in the Group."

Westfield chairman Frank Lowy said the deal was the result of the company's restructure that started in 2014.

An emotional Mr Lowy, speaking from Milan, said it was a day of mixed emotion but that he was certain he and his sons Peter and Steven had taken the right course.

"Why now? Why now because it is appropriate to do it now," Mr Lowy said.

"Firstly because it's a very good price for our shareholders and also from our point of view and the company I think we want to change our roles in the world … we would rather be investors than executives."

"As Peter said earlier, we have worked at Westfield for a combined 145 years," he said.

Unibail-Rodamco boss Christophe Cuvillier said the deal would create significant value for all shareholders.

"The acquisition of Westfield is a natural extension of Unibail-Rodamco's strategy of concentration, differentiation and innovation. It adds a number of new attractive retail markets in London and the wealthiest catchment areas in the United States."

Lowys had been concentrating on foreign investments

The Lowy family will retain control of Westfield's retail technology platform, OneMarket, which will be spun off into a new company on the ASX, with Steven Lowy remaining as chairman.

Under the terms of the deal, the Lowy family will retain a significant holding in the merged operation, given two thirds of their $2.7 billion windfall will be delivered in stock.

Mr Lowy has engineered several major reshuffles of his corporate empire in the past decade, the most recent one his controversial move to hive off the Australasian assets into a separate listed company called Scentre in 2014.

Scentre, which is not in a trading halt, closed up 4.1 per cent at $4.35.

Mr Lowy and his two sons Steven and Peter, who are joint chief executives, abandoned most of their investment in the Australian malls, to concentrate on the international corporation.

Westfield Corporation runs 45 shopping centres and airport retail precincts in the US, UK and Italy, including the retail space in the new World Trade Centre in New York.

Westfield suffers from US mall decline

Westfield shares were worth $8.50 when they last traded, valuing the company at $17.6 billion on the ASX.

Joint chief executive Peter Lowy explained that real estate investment trusts globally had been treated harshly by investors in the past year and all were trading at a discount.

Given the large premium offered by Unibail, Peter Lowy said this deal allowed Westfield investors to make up that shortfall.

"When you look at the transaction and you look at the price that Unibail has agreed to pay, we have taken that gap from where the stock was trading back to the value of the company," he said.

Mr Lowy injected close to $180 million of his family's cash to top up his Westfield Corporation stake during the demerger, taking the family holding in the international group to a little under 10 per cent.

Since then, its shares have gyrated, recovering through 2015 and 2016 as the US economy began to improve.

But its stock has fallen nearly 10 per cent so far this year, leaving it with only modest gains since it split from the Australian operations.

Retailers across the United States are in what appears to be terminal decline as shoppers abandon traditional bricks and mortar while the digital revolution lays waste to traditional shopping.

That, in turn, has begun to harm shopping malls as retailers have struggled to pay rents with many closing down their outlets.

Thousands of mall-based stores have shut their doors across the US this year, including stalwarts such as JC Penney, Macy's, Sears and K-Mart reducing their physical footprint.

Smaller retailers such as Payless and RadioShack have been among the hardest hit.

That, in turn, has begun to affect employment. Until as recently as two years ago, shopping malls were providing America with 200,000 extra jobs a year, but that trend has now suddenly reversed.

According to the latest Bureau of Labour Statistics, the retail industry has lost an average of 9,000 jobs a month this year. This time last year, malls provided jobs growth of around 17,000 a month.