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Incandescent light bulbs are officially banned in the U.S.
(www.digitaljournal.com)
This is a most excellent place for technology news and articles.
I can't find such a study, and it seems extremely unlikely to me that any such study was performed recently. The original law was passed in 2007, and then the regulations were in political limbo for more than a decade.
My base hypotheses here, subject to easy refutation by any real evidence, are that: