Auto insurance rates that fell sharply after deregulation in Massachusetts are climbing again. Five years after the state began to allow insurers to set their own rates, the average premium was about the same as it was before the change. According to figures from the state Division of Insurance, premiums dropped about 12 percent between 2007 and 2009 to a statewide average of $861, saving the average motorist about $122 per year. By 2012, the average premium was back up to $974, only $9 less than what it was before deregulation. 2012 was the most recent year that statistics were available. State officials say deregulation has helped consumers by offering more choice. The number of companies offering auto insurance in Massachusetts has nearly doubled.