4.9 Income tax expenses

in CHF thousand   2017   2016
Current income tax   4,401   3,903
Deferred income tax   2,588   3,023
Total income tax expenses   6,989   6,926

The income tax expense on the Group’s earnings before tax according to the profit and loss statement differs from the theoretical amount calculated by applying the weighted average interest rate of the Group to the Group’s earnings before tax as follows:

Calculation of income tax

in CHF thousand   2017   2016
Earnings before income taxes   13,385   19,257
Weighted average group tax rate   16.7%   21.7%
Expected income tax   2,231   4,170
Effect of change in local income tax rates     60
Non tax-deductible expenses   266   163
Tax-exempt income     –149
Use of tax losses carried forward   –679  
Effect of tax loss carry-forwards not capitalized   2,533   1,056
Capitalization of previously not recognized tax loss carry-forwards   –5  
Impairment of capitalized tax loss carry-forwards   2,761   84
Tax effects relating to other periods and other tax effects   –118   1,542
Effective income tax expense   6,989   6,926

Non-capitalized tax loss carry-forwards and impairment of tax loss carry-forwards primarily concern the Industrial Systems segment. See also note 4.2.