Over the last decade, as luxury retailers large and small grew to accept — then embrace — e-commerce, most Swiss watchmakers struck a tone of defiance, vowing to protect their timepieces from the perils of the internet.

This week, with the Baselworld luxury watch and jewelry fair drawing industry executives and watch fans from around the world, many brands, chastened by declining sales, would have to acknowledge they were wrong. They have joined an ever-growing number of high-end companies now convinced that selling online is crucial to capturing the next generation of buyers.

Jules Boudrand, a Geneva-based director at the consulting firm Deloitte, said, “We did a consumer survey in six different countries, and for people between 18 and 30 years old, social media is clearly becoming the most important marketing channel, and they have a high intention of buying watches online.”

He said that half of the watch executives surveyed as part of the 2016 study said they would emphasize online resellers more than any other sales channel this year, compared with only 19 percent in 2015.