(a) The commissioner shall carefully examine the tax digests of the counties filed in his office. Each digest for a county in a digest review year shall be examined for the purpose of determining if the valuations of property for taxation purposes are reasonably uniform and equalized between counties and within counties.

(b) For any digest in any digest review year where the digest for the preceding digest review year was conditionally approved by the commissioner, the commissioner shall also carefully examine the digest to determine if it satisfactorily corrects the deficiencies that resulted in the digest for the preceding digest review year being conditionally approved.

(c) For each year, including each year that is not a digest review year for the county, the commissioner shall utilize the overall assessment ratio for the county as provided by the state auditor.

(d) It shall be the further duty of the commissioner to examine the itemizations of exempt properties appearing on the digest and, if in the judgment of the commissioner any properties appearing on the digest are subject to taxation, to so advise the board of tax assessors of the counties concerned with an explanation of his reasons for believing the property is subject to taxation.