Thasos, a company that specializes in gathering location data from cellphones, has used that information to rank REITs that specialize in retail properties.

Unibail-Rodamco-Westfield is the best-performing REIT among those that hold enclosed retail properties, followed by Taubman Centers, Macerich, Pennsylvania REIT and Simon Property Group, according to Thasos' ranking.

Among those REITs that hold open-air retail properties, Thasos said that Urstadt Biddle Properties enjoys the best performance, followed by Washington REIT and Saul Centers.

New York-based Thasos produced its ranking using a methodology of its own creation. The company uses mobile phone location data, which it said is anonymized, to determine where visitors to a property actually come from, which it calls a "Thasos Trade Area."

The company said it is then able to analyze that visitor data with Census Bureau data (about the places those visitors are from) to score properties according to six performance indicators, including visitation growth, loyalty, household income, property value, educational attainment and household density.

The data is generated for over 95% of the retail properties owned or operated by the largest publicly traded U.S. REITs. Thasos then ranks the REITs by the performance of the properties in their portfolios according to Thasos' metrics.

According to Thasos, its method is more accurate than the traditional technique of drawing a ring around a property (such as a 5-mile radius) and then evaluating a property based on the demographics of everyone within the ring, since not everyone visits a particular property.

Besides using the data to rank retail REITs, Thasos said its data crunching has allowed the company to make a few observations about the state of retail real estate.

For example, foot traffic growth at U.S. malls starting in late 2017 has peaked and begun to reverse course in recent months. Also, grocery-anchored open-air malls continue to outperform all other mall categories, but the margin of this outperformance narrowed significantly in 2018.

Experiential tenants — including Tesla, Apple, Eataly, Starbucks Reserve and other high-end destinations — have yet to provide a meaningful edge in year-over-year visitation growth, Thasos said.