I work 8 hours a day and commute 2
I do 99% of the cooking (Mr Smith grills out sometimes)
I do 99% of the laundry, house cleaning, and repair work. (Mr Smith does take care of the mower.)
I probably average 30 hours a week, every week, on unpaid work...but some weeks, I put in a lot more time.
Mr Smith works a lot of overtime... but home time, except for the mowing and trimming, is almost 100% down time for him.
I have severe doubts about the OP. 
In my household, I would say that my husband and I work equally. He helps me clean the house. He knows I don't do dishes, even though we have a dishwasher, and he has no problem doing that. Plus he takes out the garbage and vacuums quite regularly. He also does about 50% of the cooking and ALL of the yardwork. I do the laundry, sweep, mop, dust, toilets, and bathtubs. We share our parenting duties quite equally as well. Although, my baby girl is in a stage now where no one but mama will do.
My husband's paid job is probably more physically demanding than mine, and he has to deal with all of the client relations, but my job is more mental, so we are probably equal there as well. He may have a little more on me in that department.
So, for me, this study tends to be true. And probably for all my friends as well, but we are of a younger generation, and things have changed a lot. Anyway, I can see how it wouldn't be true for many.