WASHINGTON (MarketWatch) — Housing-market activity in September hit its second highest in eight years, fueled by low mortgage rates, continued jobs growth and a slight improvement in credit availability, a trade group said Thursday.Existing-home sales rose 4.7% to a seasonally adjusted annual rate of 5.55 million, the second highest level in eight years, the National Association of Realtors reported. Economists polled by MarketWatch had forecast a 5.34 million annualized sales rate. Compared with a year earlier, sales were up 8.8%.It’s important to note the data are seasonally adjusted; activity always peaks in the spring and summer, and, based on raw numbers, activity fell by 6.5%.That said, the September data indicated a continued recovery in the housing market. Mortgage rates have remained below 4% for weeks, and the unemployment rate has dropped to 5.1% from a peak of 10%. In addition, the NAR is detecting signs that the credit situation is improving.