Context: Despite these criticisms, Comcast has appeared on multiple "top places to work" lists. In 2009, it was included on CableFAX magazine's "Top 10 Places to Work in Cable", which cited its "scale, savvy and vision". Similarly, the Philadelphia Business Journal awarded Comcast the silver medal among extra-large companies in Philadelphia, with the gold medal going to partner organization, Comcast-Spectacor. The Boston Globe found Comcast to be that city's top place to work in 2009. Employee diversity is also an attribute upon which Comcast receives strong marks. In 2008, Black Enterprise magazine rated Comcast among the top 15 companies for workforce diversity. Comcast was also named a "Top 2014 Workplace" by the Washington Post in their annual feature.

Question: On what aspect did Black Enterprise Magazine name Comcast a top 15 employer?

Answer: workforce diversity