Mac laptop sales are taking off, and it’s only going to get better.

That’s what data released earlier this week by ChangeWave Research seems to be saying. ChangeWave, a Rockville, Md.-based company that conducts surveys of business executives and professionals in more than 20 industries, just released the results of its Aug. 1-8 survey on computer sales.

According to the ChangeWave data, Apple laptop sales over the previous 90 days rose from 12 percent in the June survey to 17 percent while desktop sales dropped slightly from 8 to 7 percent. I would guess that the anticipation of new iMacs (unveiled August 7) stunted sales slightly in the most recent survey. ChangeWave also asks about planned computer purchases. Here Apple laptops remained steady at 28 percent, with desktops actually rising one point from 22 to 23 percent.

Far more compelling than the changes since June is the steady growth in the Mac numbers since January 2006. Back then Apple’s laptops and desktops both comprised just 4 percent of sales over the previous 90 days. The laptop numbers have quadrupled in just over 18 months, while the desktop numbers have doubled.

In the planned purchases survey, laptops stood at 13 percent and desktops at 11 percent back in January 2006. Both of these numbers also have more than doubled.

Long-time Mac users who recall Michael Dell’s infamous 1997 insult should relish Dell’s numbers from the survey of purchases over the previous 90 days. Dell’s laptops have sunk from 44 percent in January 2006 to 30 percent in the most recent survey. But hold your jeers and taunts until you read this: Dell desktops have plummeted from 43 percent to 24 percent.

This is all fantastic news for Mac fans, but can we trust these numbers? The ChangeWave data is not based on a conventional survey of randomly chosen respondents, but rather a periodic survey of a select group of people. ChangeWave describes them as “10,000 strategically positioned experts.” I’m not an expert on polling, so I can’t say if that makes this data more or less relevant. But when you look at this survey in the context of previous computer sales data that also points to ever-growing Mac sales, especially of the laptops, you see a trend confirmed.

My instinct is that a survey of business executives and professionals about computer buying should at least indicate which way the sales winds are blowing. If there’s any weight at all to this ChangeWave survey -- and I believe there is -- those winds are plainly at Apple’s back.