When the average house or a condo is bought or sold, the real estate transaction is public. When so-called luxury units are purchased, according to a new report, there may be less transparency about the buyer. The Institute for Policy Studies — a 50-plus-year-old progressive think tank based in Washington, D.C. — is raising flags about Boston's luxury housing boom, at a time when Boston has multimillion-dollar units for sale in new and future towers. The report raises questions about whether Boston is becoming a hub for money laundering and whether the city's skyline is being taken over by developers who will increase land values and housing costs across the city. Guests: Chuck Collins, director of the Program on Inequality and the Common Good at The Institute for Policy Studies. David Begelfer, CEO of NAIOP Massachusetts, a commercial real estate development association, which represents the interests of real estate developers. Listen to the segment here.