MARBLEHEAD – Selectmen have authorized the Board of Assessors to set a Fiscal 2012 tax rate of $10.52 per $1,000 valuation, a 31-cent increase over this year.According to a report the Board of Assessors gave to selectmen at a joint meeting Wednesday evening the total valuation of the town has dropped once again, from $5.03 billion to $5.01 billion on Jan. 1, 2011 – but based on past years? reports that appears to be the smallest Marblehead drop since the real estate market began to skid in 2006.Homes make up $4.8 billion of this year?s total value, or about 96 percent. New growth made up $29.6 million.The median single-family home was assessed at $488,000, an increase of $5,000 or 1 percent. The median single family tax bill under the proposed tax rate will be $5,134, an increase of $203 or 4 percent.The average single-family home assessment was $661,384. That represents an increase from last year of $7,884 or 1.2 percent, and the tax bill on that home under the proposed tax rate will be $6,958, an increase of $286 or 4 percent.The proposed tax rate covers about $700,000 added to the town?s expenses by last June?s successful debt exclusion override votes. That amount added 12 cents to the tax rate, according to Board of Assessors Chairman John Kelley.As usual the selectmen rejected discounts on open space, small businesses and vacation homes, which state law requires them to discuss and vote on every year. They also refused to set a mathematical factor that would allow the assessors to tax business property at a higher rate than residential property.Assistant Assessor Michael Tumulty told the selectmen that factor “tends to be disproportionate.”