The movement of the magnetic North Pole is not constant and it can vary from year to year. Its movement is determined by changes in the Earth's magnetic field, which is generated by the motion of molten iron in the Earth's outer core. This motion is influenced by a variety of factors, including the rotation of the Earth, the motion of the Earth's crust, and interactions with the Sun and other celestial bodies.

Over the past century, the magnetic North Pole has been moving at an average rate of about 10 kilometers per year. However, this rate has been increasing in recent years, and the pole is currently moving at a faster rate, averaging about 50 kilometers per year. This means that the difference between magnetic north and true north (known as magnetic declination) is also changing at a varying rate.

The World Magnetic Model (WMM) is updated every five years to account for these changes in the Earth's magnetic field, and smaller updates are made in between. The most recent update to the WMM was in December 2019, and the next update is scheduled for 2024.

[color=blue]does it move at a constant rate or a varying rate[/color]

As noted in the last post, it moves all over the shop, (generally) in a small sort of way, and the rate varies significantly with time. Hence the background effort to keep a close eye on the position and refine predicted movement in the short term.

There are plenty of useful links on the net on the subject so you can read away to your heart's content. One, at random, https://www.ncei.noaa.gov/news/tracking-changes-earth-magnetic-poles, should provide some time over a coffee or two.