In another thread I mentioned that I expected a 26" wide, 1.5" benchtop to vary in width by only 1/8" over time in my shop. I understand that this is not a realistic expectation for someone living in, say, New York or Seattle, where the average relative humidity is much higher.
I'm attaching a Word document that I wrote a while back for a woodworking class where I wanted to assess what I could expect in terms of shrinkage or expansion over time in Colorado. The paper is the basis for my 1/8" estimate. I would expect the number to be higher in a climate with more humidity. If you are looking to predict wood movement in your climate, you might find the methodology useful.