On April 23, 2014, Slim took control of Telekom Austria, Austria's biggest phone carrier, which has telcos in countries such as Bulgaria, Croatia and Belarus, under a 10-year agreement, was Slim's first successful business acquisition in Europe. In a syndicate holding structure the Austrian state holding company OIAG's 28 percent are combined with Slim's 27 percent ownership. America Movil will spend as much as US$2 billion to buy out minority shareholders in a mandatory public offer and invest up to 1 billion euros (US$1.38 billion) into the company, which it sees as "platform for expansion into central and eastern Europe". Labor representatives boycotted attending the OIAG supervisory board meeting for 12 hours criticizing lack of explicit job guarantees.
In July 2014, Slim invested in WellAware, a Texas-based oil and gas software developer, this investment was also made with former Republican vice president Dick Cheney. External funding was provided by Activant Capital Group and Slim, along with participation from strategic investors and WellAware board members Ed Whitacre. When Mexico eventually prepared to open its oil and gas sectors to domestic and foreign private capital for the first time in 75 years, it has been widely speculated that Slim will play a major role toward contributing to Mexico's new energy landscape. Slim's investment in WellAware, whose software allows oil and gas companies to track wells and pipelines remotely and collates data for making forecasts, adds to a number of oil-related investments that he has been making in the past years in Mexico, Latin America and the United States.
On July 15, 2014, Forbes announced that Slim had reclaimed the position of the wealthiest person in the world, with a fortune of US$79.6 billion.
In September 2014, Forbes listed Slim as number 1 on its list of billionaires with a net worth of US$81.6 billion.
In May 2014, Slim opened Inbursa Aquarium, Latin America's largest aquarium. Slim owns the Duke Seamans mansion, a 1901 beaux arts house on 5th Avenue in New York City, which he bought for $44 million in 2010. The mansion is 20,000 square feet and has 12 bedrooms, 14 bathrooms, and a doctor's office in the basement. In May 2015, he listed the property for sale at $80 million, nearly twice what he had paid. In April 2015, Slim bought the Marquette Building in Detroit and purchased PepsiCo Americas Beverages headquarters in Somers, New York for US$87 million. Slim owns a second mansion in New York City at 10 W. 56th St, which he leased early in 2015 to the John Barrett Salon for US$1.5 million annually. The property was bought in 2011 for US$15.5 million.
Slim's growing fortune has been a subject of controversy, because it has been amassed in a developing country where average per capita income does not surpass US$14,500 a year, and nearly 17% of the population lives in poverty. Critics claim that Slim is a monopolist, pointing to Telmex's control of 90% of the Mexican landline telephone market. Slim's wealth is the equivalent of roughly 5% of Mexico's annual economic output. Telmex, of which 49.1% is owned by Slim and his family, charges among the highest usage fees in the world, according to the Organisation for Economic Co-operation and Development. The average Mexican spends 1.50 pesos per day on Slim's goods and services for a total of roughly US$140 million a day and the Federal Telecommunications Institute, a new Mexican government anti-monopoly watchdog said in April 2014 that Slim's telecom businesses are monopolies. Slim's business presence in Mexico alone is so broad that many Mexicans find it appropriate to call the country "Slimlandia" as it is almost impossible to go a day in Mexico without contributing to Slim's wealth.