Extensive change along Madison Avenue continues with 18 businesses springing up on or just off the luxury venue in the first half of the year and another 11 expected in the second half.

Among the openings between 57th and 86th Streets were Aquazzura shoes, 939 Madison Avenue; De Beers Diamond Jewellers, 777 Madison Avenue; Isabel Marant, 23 East 67 Street; Rag & Bone, 11 East 68 Street, and Sonia Rykiel at 816 Madison Avenue.

Coming soon: Brioni at 680 Madison Avenue; Elie Saab, 860 Madison Avenue, and Stella McCartney, 929 Madison Avenue.

Major retail expansions under way include Bally, 689 Madison Avenue; Bottega Veneta, 740 Madison Avenue; Dominique Levy, 909 Madison Avenue, and Roland Mouret, 1006 Madison Avenue.

There’s also construction under way at 706, 680 and 935 Madison Avenue.

Businesses completing expansions this year included Jimmy Choo, 699 Madison Avenue; Christian Louboutin, 965 Madison Avenue; Giuseppe Zanotti, 806 Madison Avenue, and Di Donna Gallery at 744 Madison Avenue.

“The first half of 2016 was a period of intense investment on Madison Avenue,” said Matthew Bauer, president of the Madison Avenue Business Improvement District, which extends from 57th to 86th Streets. “The strength and stability of the local consumer market, as well as the international visitors drawn to the area by our five world-renowned hotels and the upper East Side’s many cultural institutions, provide a unique client base distinct to our district.”

Other luxury venues are more dependent on tourist spending, which has been weak all year, particularly among Chinese, Brazilian and Russian visitors. While tourists are spending less, they are traveling in record numbers.

Eighteen openings in a six-month stretch is not a record for Madison Avenue, though it is more than has been seen in awhile, according to Bauer. “Typically, there’s about a dozen,” Bauer said, noting there were 10 openings in the second half of last year, and 11 in the first half. Madison Avenue saw 27 openings in 2014, 30 openings in 2013 and 39 openings in 2012.

Bauer, describing Madison Avenue as holding steady, said there were 14 closures this year, but there have been more openings than closings. He put the vacancy rate at 6.8 percent between 57th and 86th Streets, and 5.1 percent between 57th and 72nd Streets.

Retail rents have been dropping, coming off recent record-high prices and landlords seeing some softening in demand. Any rent decline makes Madison Avenue more appealing to prospective tenants.

“Overall around the city, there has been a decline in rents,” Bauer said. “We [Madison Avenue] are down 3 percent from spring 2015. Other corridors were actually down in the high single digits. The drop on Madison Avenue is not as big as other parts of the city. The demand is still strong.”

The asking rent for ground-floor space along Madison Avenue between 57th and 72nd Streets declined 3 percent, to $1,613 a square foot, from $1,644 in spring 2015, according to the Real Estate Board of New York’s spring report.

Other openings in the first half of 2016 included: Aurelie Bidermann, Iro, Moynat, Smythson of Bond Street, Veronica Beard and The Row.

Madison Avenue got a lift in March with the launch of the Met Breuer Museum at 945 Madison Avenue, on the site of the former Whitney Museum of American Art.

“The luxury marketplace worldwide has had some difficult times. But the Madison Avenue market is a bit less fickle because it has this very strong local base,” Bauer observed. “We are seeing a lot more stores open up till 7 and a lot more open on Sundays — easily half are opened Sundays. Ten years ago, it was 25 percent.”