Apple Inc.’s iPhone sales declined about 5% globally in the final quarter of last year, hurt by underwhelming upgrades and competitors making inroads in China.

Phone sales are losing ground while the industry is growing worldwide. Success in China is particularly important to Apple's future.

Multiple research firms say Apple Inc. saw its iPhone sales fall by about 5% globally in the final quarter of last year. Apple’s artificial intelligence software, called Apple Intelligence, failed to stir up strong demand,