Annually, on or before the third Monday in August, the county auditor shall transmit to the directors of the district a written statement showing separately the total value of all lands within the district subject to assessment and the total value of all such lands in any portion of the district within which a different rate of assessment is to be levied. The values so reported shall be those obtained from the assessment books of the county as last equalized and corrected together with an estimate of the values of the lands within the district subject to assessment by the State Board of Equalization.