Broadway sales slipped slightly last week — but then, a number of shows were saving up for this week.

Of the 34 productions on the boards, 20 of them only played seven perfs rather than the usual eight during the frame that included Christmas Day. (One previewing show, “The Road to Mecca,” only played six.) The week’s darkened showtimes helped bring the Rialto cume down by about $1 million for $23.3 million.

But this week, of course, a number of shows will tack on an extra perf to take advantage of the tourist boom that hits Broadway during the sesh between Christmas and New Year’s, traditionally the most profitable frame of the year. Last year during the same week, about a dozen productions played more than the usual eight.

Last week, in any case, a couple of shows managed to uptick despite playing one fewer perf — most notably “Godspell” ($341,203), which climbed by about $50,000 in a rise likely fueled by the high profile of the title and its family-friendly resonance with the Yuletide season.

The frame also underscored which shows reap the heftiest proportional benefits when tourists are in town. Perennial “The Phantom of the Opera” ($1,038,045) jumped up by a whopping 36% and “Mamma Mia!” ($704,380) stepped up by 26%, with both musicals playing the usual eight shows.

Meanwhile, “Wicked” ($2,107,015) once again broke the $2 million mark while at the same time reconquering the top 10, besting challenger “The Lion King” ($1,981,442). “Wicked” and “Spider-Man: Turn Off the Dark” ($1,759,850) posted gains of 20% each.

Among the declines reported along the Main Stem, the most notable was at “On a Clear Day You Can See Forever” ($351,294), plummeting by nearly $400,000 (or 53%), a fall of such severity that the production’s seven-perf week can’t explain all of it. It remains to be seen whether the slump is a holiday blip for a show that doesn’t seem to have the feel-good tourist appeal of big-title offerings, or whether it’s a mark of challenges ahead as the show heads into the traditionally rough month of January.

Among other recently opened musicals, the soon-to-shutter “Bonnie and Clyde” ($248,221 for eight shows) hasn’t yet seemed to benefit from any last-minute sales while “Lysistrata Jones” ($132,779 for seven), a new comedy without much title or cast recognition, continues to struggle.

On the upside, though, tuner “Porgy and Bess” ($671,901) took a nice leap forward, playing seven previews in advance of its opening next month. Figure seems solid for a new, serious-minded revival competing against the razzle-dazzle fare more likely to pull attention during the holidays.