Do I use the current years home & land value or the home & land value when I started using my Home Office for Form 4562?

Turbo Tax wants to know about my home for asset depreciation form 4562 for a Home Office. I have always used my current structure & land value on my property tax statement. Is this the correct figure to use? 
Or am I supposed to be using the same Structure & Land value year after year from the year I started using my Home Office?