WASHINGTON (MarketWatch) — Confidence in the market for newly built single-family homes dipped slightly in September to remain in very low territory, according to an index released Monday. The National Association of Home Builders/Wells Fargo Housing Market Index fell by a point to 14, on a seasonally adjusted index where readings above 50 are considered good. The index, which correlates closely with single-family housing starts, has held between 13 and 16 for the last six months.