By Neil Hughes

Published: 03:10 PM EST (12:10 PM PST)

Mac sales a year ago were exceptionally strong, making Apple's year-over-year sales increase in April 2011 a "soft" 9 percent.

A tough comparison in the month of April led to the low number seen in the latest NPD domestic sales data, which is well below the 22 percent year-over-year increase investors on Wall Street are expecting. April is the first of three months in Apple's June quarter.

Analyst Gene Munster with Piper Jaffray said on Monday that despite the slow start, it is "too early to make a call" based on just one month of data for the U.S. only. He believes that with international sales included, the Mac is likely tracking in line with expectations.

Wall Street watchers expect Apple to sell between 4.1 million and 4.3 million Macs total in the June quarter, or around 22 percent more than the company moved a year ago.

Last April, Mac sales were up 38 percent year over year in a particularly strong month of 2010. Apple will face another tough comparison in May, when Mac sales were up 35 percent in 2010.

But Munster noted that comparisons ease "dramatically" in June, when sales were up just 11 percent year over year in 2010.

The Mac sales boost in 2010 was caused by the release of new MacBook Pros in April of last year. For comparison, Apple updated the MacBook Pro line again, adding the high-speed Thunderbolt port in late February. That refresh caused sales to spike 47 percent year over year in March.



For the rest of 2011, domestic Mac sales saw a 20 percent year-over-year increase in January, and 12 percent in March.

The latest NPD data for the U.S. also suggests Apple will sell between 8 million and 8.5 million iPods in the June quarter. The sales figures show iPod sales tracking down 6 percent year over year, though sales for the full three-month quarter are expected to be off between 10 percent and 15 percent from 2010.