Chris, it's worse than you think.  <img src="images/graemlins/wink.gif" alt="" />  The earth's magnitic pole is quickly drifting north, approx 40km/yr., through the Canadian arctic and will end up in Siberia in a few decades!  
NASA had a very informative article on this subject,  
Earth's Inconstant Magnetic Field . It also discusses the periodic magnetic pole flip-flop and the gradual weakening of our magnetic field.  
Compass makers better be prepared.  Here's an image of the magnetic fields today and what it might look like during a reversal. 
 
 How would you set declination then????   <img src="images/graemlins/grin.gif" alt="" />