New numbers of analyst firm NPD for March added to previous data for the quarter suggests that US Mac sales will be flat or low in terms of year-over-year growth, missing analyst's estimates, warned Piper Jaffray's Gene Munster. Foreign sales, already expected to offset the slow growth in North America as buyers wait for anticipated notebook and iMac refreshes, may not hit the 14 percent year-over-year consensus targets analysts expect.