Source: Needham. Click to enlarge.

FORTUNE — Although Mac shipments grew faster than the overall PC market in calendar Q3 for the 25th quarter in a row, Needham’s Charlie Wolf sees cause for concern in latest data.

In his regular quarterly review of Apple’s AAPL Mac business, he notes:

  • The difference in Mac vs. PC growth rates — up 1.9% for the Mac compared with down 2.5% for all PCs, including Macs — is smaller than in previous quarters
  • Mac shipments to education fell 0.1% while overall PC sales to schools fell nearly 13.9% — the first definitive evidence, Wolf writes, that the iPad is cannibalizing PC sales in the U.S. (Apple sold nearly 1 million iPads to U.S. schools in the quarter.)
  • Overall PC shipments to the home rose 1.1% worldwide in Q3 while Mac shipments to the home fell 4.6%, an outsized decline Wolf attributes to delays in the Mac upgrade cycle.
  • The best news for the Mac: It continues to thrive in the business market. Mac units grew 56.6% in the U.S. even as overall PC sales fell 8.8%s. Worldwide, Mac business shipments increased 22.1% compared with a 4.5% decline in overall business sales.

“Notwithstanding its premium prices compared to the prices of Windows PCs,” Wolf concludes, “we expect that the Mac will continue to grow faster than the PC market, propelled by the twin halo effects emanating from the iPhone and iPad.”

Below: Three more charts from Wolf’s report.