* Manufacturing output data trails market expectations
* Jobless rate dips to lowest in at least 3 years
* November's copper output picks up on better ore grades
By Antonio De la Jara and Moises Avila
SANTIAGO, Dec 28 (Reuters) - Chilean manufacturing output grew a weaker-than-expected 0.8 percent in November from a year earlier, dampened by sluggish external demand and fewer working days, the state statistics agency said on Friday.
The relatively new index, broadly comparable to the prior industrial output index, fell a seasonally adjusted 3.5 percent in November from October, after surging the previous month on the back of extra working days.
Analysts and economists in a Reuters poll forecast manufacturing production growth of 2.6 percent year on year.
The index surged 9.1 percent in October from a year earlier, the biggest annual gain in 2012, and jumped a seasonally adjusted 19.7 percent in October from September.
Chile's small, export-dependent economy has generally fared better than expected despite slowing demand from top trade partner China and fallout from the euro zone crisis.
Despite the impact of softer external demand in Friday's factory data, food and wood paper production remained buoyant.
The South American country's jobless rate for the September-November period fell to 6.2 percent, its lowest level in at least three years, due to robust economic growth, strong domestic demand and an expansion of seasonal farm jobs, the government said.
The jobless rate has been calculated using a new methodology since early 2010. Using the prior system, the September-to-November unemployment rate is the lowest in six years.
Agricultural jobs traditionally increase in the southern hemisphere's spring and summer months.
The unemployment rate was expected to remain steady at 6.6 percent, according to the median forecast of nine analysts and economists polled by Reuters.
Chile's jobless rate for the September-to-November period last year was 7.1 percent.
With regard to copper production in the world's top producer of the red metal, output rose 2.6 percent in November, year on year, to 478,545 tonnes of copper.
The improved output was due to better mineral ore grades at some mines and a production ramp-up at mines that started operations last year, the INE statistics agency reported.
Copper production expanded 3.7 percent to 4.94 million tonnes between January and November, compared with the year-earlier period. Compared with October, output grew 0.5 percent.
Chile is struggling with dwindling ore grades in many of its aging deposits, although new mines have helped increase output this year.
A recovery in the world No. 1 copper mine, Escondida, majority owned by BHP Billiton Ltd , as well as higher output from Anglo American Plc's disputed Los Bronces mine are boosting Chile's production.
Output of molybdenum, a metal used to harden steel, rose 3.6 percent to 2,790 tonnes in November, the INE said. January-to-November production of molybdenum dropped 14.7 percent versus the same period a year ago to 28,571 tonnes.