Odd Appraised Land vs Building "Adjustment" in 2010/2011

[Tim Andersen]

Hey all, first of hopefully many posts here on BiggerPockets!  This first one's more just a curiosity with something I noticed recently while looking into the "numbers" in my own neighborhood and my own house in Fairway, Kansas (not that I want to sell or rent my own house at this point...just needed a starting point for "numbers").

Curious about appreciation of my own house, I was able to find a way with the county website to get the last 15 years worth of property value.  So I collected the data in a spreadsheet to better analyze it (maybe there are websites that do this for you but it was easy enough to do on my own for one property).  

Breaking the land vs building values down per year, I found what seems to me to be an odd "adjustment" or "shift" of value from the year 2010 to 2011 where my land value shot up an unusually high amount but my building value lowered by an equal amount, leaving a net change of 0.

The image below shows the situation.  I've "faked" my actual land/building numbers as I'd prefer to not to share my personal home values on the web, but the ratios between land and building are accurate and a good representation of the situation.

So not that it really matters (I think), but I'm just wondering if anyone might know--why the sudden shift in value between land and building?  Has anyone else seen something like this happen with your own properties?  I understand land goes up and down and so does a building's value.  But it seems a little too convenient that the total change levels out to the same value in the end.  There must be something more to this, so just looking for possible explanations which I can't think of.

Thanks!
Tim