Even amid a decline in U.S. PC shipments, Apple continues to see steady shipment growth, according to new PC shipping estimates from Gartner. Apple shipped nearly 1.7 million PCs in 1Q15, up from 1.5 million in 1Q14, marking an 8.9 percent increase. Overall PC growth in the United States in 1Q15 was down 1.3 percent compared to 1Q14, with Dell and other smaller manufacturers seeing a decline in shipments. Gartner estimated total PC shipments in the U.S. during 1Q15 at 13.9 million, down from 14 million last year.

During the quarter, Apple captured 12 percent of the market, up from 10.9 percent in the year ago quarter. Apple is positioned as the third largest PC vendor in the United States, and continues to trail both HP and Dell when it comes to market share.

Gartner's Preliminary U.S. PC Vendor Unit Shipment Estimates for 1Q15 (Thousands of Units)

HP shipped 3.6 million PCs during 1Q15, garnering it 26.1 percent of the market. Dell shipped 3.2 million for 23.2 percent of the market, and Lenovo came in after Apple with 1.7 million shipments for 11.8 percent of the market. ASUS, the fifth largest vendor in the U.S., sold just under a million PCs for 7.2 percent of the market.

Apple's U.S. Market Share Trend: 1Q06-1Q15 (Gartner)

IDC also released its shipment estimates today, and as is typical, its numbers are different than Gartner's numbers, in part because Gartner counts Windows-based tablets as personal computers, while IDC does not. According to IDC, overall PC shipments in the United States for 1Q15 were at 14 million, with Apple responsible for shipping 1.6 million PCs during the quarter, up from 1.5 million in 1Q14. IDC estimates Apple saw 1.7 percent growth with 10.9 percent market share.

IDC also ranks HP and Dell as the top two vendors in the United States, but its estimates place Lenovo as the third largest vendor with Apple coming in fourth and Toshiba coming in fifth.

As for worldwide shipments, Apple does not rank as one of the top five vendors so its worldwide shipments are not broken down in IDC and Gartner PC shipping estimates. Total worldwide PC shipments for 1Q15 were at 71.7 million according to Gartner, a decline of 5.2 percent compared to the year ago quarter, while IDC estimates put total worldwide shipments at 68.5 million, a decline of 6.7 percent.

It is important to note that data from Gartner and IDC is preliminary and that the numbers can shift somewhat, sometimes dramatically. Last year, for example, Gartner predicted Apple shipments at 1.521 million, later revising the number to 1.534 million. IDC predicted Apple shipments of 1.471 PCs, while the final number was 1.559 million.