Best Buy’s first-quarter profit fell 15 percent as sagging consumer demand drove down sales, sending shares down 7.3 percent, or $2.82, to $35.84, their steepest drop since December.

Net income at the world’s largest electronics retailer dropped to $153 million, or 36 cents a share, in the three months ended May 30. Sales at stores open at least 14 months fell 6.2 percent, far worse than a 2.3 percent drop predicted by Colin McGranahan, an analyst with Sanford C. Bernstein.