1989 is way out of date-that was 20 years ago, so the current dec sounds right to me.
This NOAA website is even better-
http://www.ngdc.noaa.gov/geomagmodels/struts/calcDeclinationYou can set the year and see not only the dec for that year, but the rate of change as well, which isn't constant.
The dec in my GPS is from 1990 and it is decreasing at a rate of 5'W per year. In 1990 it was 14 and decreasing at only 1' per year.
Now my dec is 12 Deg 45', so it has changed by 1 Deg, 15' W in 20 years. The rate of change will also depend on where you are.