Clark County’s population growth continued to lose steam in the past year, slowing to its lowest rate since 1970, the latest state population estimates show.The county grew by 0.6 percent, or 2,637 residents, to a total of 428,000 between April 2010 and April 2011, according to the annual July 1 report by the state Office of Financial Management.That’s a considerable slowdown from last year and the year before, when growth stood at 1 percent and nearly 1.7 percent, respectively, but it’s nearly identical to the state’s rate of growth. The state added just 43,360 residents to reach nearly 6.8 million.“Growth is slow everywhere,” said Yi Zhao, the state’s chief demographer.Zhao blamed the deceleration on the economic downturn. Although the recession technically ended in 2009, there have been no signs of a quick recovery.Limited job opportunities and a sluggish housing market hamper migration to the area, she said.“One of the primary reasons people move is to take a job or move to a place where jobs are more plentiful,” said Scott Bailey, regional economist for the Washington Employment Security Department. The county’s jobless rate in May was estimated to be between about 10 percent and 13 percent.The economy also appears to have influenced more women to delay having children. The county’s births decreased by 500 to a total of 5,000 in the past year, similar to the trend statewide.