Waaay back when I was in the Air Force and building flight plans for F4s, it was part of the routine to read the magnet variation lines on the navigation charts, sometimes in the range of +18 degrees There was also usually a statement to the effect "variation changes +x degrees per year", such that you also had to check the date the chart was printed and add or subtract additional variation to your calculations. This was in the early 70s, and obviously this is nothing new. Same for marine charts.
What amazes me is that there are people who aren't aware of magnetic variation at all...