By comparison, sales of all homes in the major markets tracked by Redfin declined by 1.2 percent.
"The luxury housing market was the first to recover after the crisis and has been growing strong ever since," said Nela Richardson, chief economist at Redfin.
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Inventory at the high end remains tight in many parts of the country. The number of homes for sale in luxury ZIP codes for $1 million or more has dropped by 13 percent from last year. Inventory is down even more for more expensive homes: The number of $5 million-plus homes for sale in luxury ZIP codes is down 47 percent from last year.
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The three most expensive sales of the quarter were all above $25 million. A home in Malibu, California, was the top seller, at $33.5 million. The runner up was a home in Indian Creek, Florida, which sold for $28 million; a home in Armonk, New York, sold for $27.5 million, according to Redfin.