if you thought the Bay State’s flat population growth meant more room for parking, forget it. According to the state Department of Revenue, the number of registered passenger vehicles in Massachusetts grew 6.6 percent from January 2000 to January 2005, while the number of people living here crept up by 1.1 percent over roughly the same period. As shown in the larger map below, the number of vehicles per capita is highest in resort areas (Cape Cod and the Islands, the Berkshires), presumably because so many non-residents have cars there. But newer vehicles of all types (including motorcycles) are concentrated in Boston’s western suburbs and other communities along I-495, as indicated in the smaller map. In most communities the increase in registered vehicles during the first half of this decade ran two to seven percentage points above population change, but growth was especially high in Middleborough (up 20 percent vs. population growth of only 6 percent), Winthrop (9 percent more passenger vehicles-primarily light trucks-and 5 percent fewer people), and Everett (10 percent more carriers, 2 percent fewer citizens to carry). At the other end of the spectrum, Hingham’s fleet dropped by 3 percent even as its population rose by 7 percent.