BERLIN, Jan 19 - German producer prices in December were unchanged month on month and rose 1.8 percent year on year, in line with forecasts, statistics office data showed on Monday. Excluding costlier energy products, producer prices would have been just 0.2 percent higher than in December 2002, the statistics office said in a statement. In 2003 as a whole, producer prices were on average 1.7 percent higher than in 2002, mainly due to a rise in energy and tobacco taxes that took effect on January 1, 2003, the office added.//