If useful life is:The applicable percentage is:
4 years or more but less than 6 years ................33 1/3
6 years or more but less than 8 years ................66 2/3
8 years or more .........................................100
The useful life of any property for purposes of this section is determined pursuant to the methods as the tax commissioner may require as of the date the property is first placed in service or use in this state by the taxpayer, determined as the tax commissioner may require.
W. Va. Code § 11-13S-5