Average asking rents for apartments in the San Fernando Valley rose 7.5 percent to $1,550 per month in the fourth quarter compared to a year ago, according to data released by RealFacts, a tracking service in Novato. The largest increases took place in the one-bedroom, one-bath category where rents rose 8.3 percent to an average of $1,238. The most recent increases seemed to run contrary to the latest occupancy trends in the area, which showed occupancy decreased 3 percentage points from the year ago period to a rate of 93.5 percent after remaining relatively steady through 2005 and most of 2006. Vacancy rates were up in nearly every Valley community but the biggest changes occurred in Simi Valley, where the occupancy rate fell nearly 12 percent, and Woodland Hills, where the occupancy rate fell 7.7 percent. The community with the highest rent increase was North Hollywood, where rents rose more than 21 percent on a year-over-year basis, no doubt the result of new construction that has opened there. Also among the communities experiencing the most dramatic rent increases, Simi Valley, with an 11.8 percent increase year over year; Thousand Oaks, with an 8.9 percent increase and Northridge with an 8 percent increase.