The estimates released Wednesday by IDC and Gartner show very different pictures. In IDC's research, domestic Mac sales were off 11.2 percent year over year in the third quarter, while the overall U.S. PC market slid 0.2 percent.
Gartner, meanwhile, found that Apple's shipments slid just 2.3 percent, while the U.S. PC market was actually up 3.5 percent year over year in their models.
Regardless, estimates from both Gartner and IDC suggest that Mac sales are no longer outpacing the PC market at large, at least in America. But the numbers don't include Apple's growing international share, nor does either firm track tablet shipments, such as Apple's market-leading iPad.
Gartner's third-quarter data pegged HP as the top U.S. PC maker, with year over year growth of 4.5 percent propelling it to a 26.9 percent share. In second was Dell, up 3.3 percent and holding 21 percent of the market, while Apple's estimated 2.1 million shipped units were good for third place, with a 13.4 percent market share. That share is down from 2012, when Apple held 14.2 percent of the U.S. market.
Following Apple was Lenovo with a big 24.6 percent year over year gain and a 10.5 percent share, according to Gartner. Toshiba took fifth with a 7 percent share and a 13.5 percent gain from 2012.
IDC, meanwhile, also found the companies in the same order. But their estimates give Apple a slightly smaller 11.6 percent share of U.S. shipments. IDC estimates that Apple shipped 1.9 million Macs in the U.S. in the third quarter.
As usual, Apple did not crack the top five PC vendors worldwide in either IDC's or Gartner's data. IDC and Gartner both had the top five, in order, as Lenovo, HP, Dell, Acer, and Asus.
Worldwide, IDC estimates that PC shipments 7.6 percent to 81.6 million. Gartner's global numbers estimate an 8.7 percent dip to 80.2 million total units.