Homebuilders seem confident about the market for new single-family homes — the National Association of Home Builders/Wells Fargo Housing Market Index (aka Homebuilders Confidence Index) jumped 18% for November to its highest level since May 2010.

The bad news is that the jump seems so large because, frankly, the index is so low right now; it went from 17 to 20. That score means that 20% of builders view market conditions as “good.”

“While this second solid monthly gain on the builder confidence scale is encouraging, the overall measure remains quite low due to the many challenges that home building continues to face” said NAHB chairman Bob Nielsen.

The survey isn’t scientific, but it’s been going on for more than 20 years; builders are asked to rate their perceptions of the market and their sales expectations, and using arcane magic mathematical calculations, the NAHB turns that into a score.

Read more at www.nahb.org/hmi.