Obtaining the mean

For each age, the mean of an income group is obtained by adding its value to the values of its adjacent groups to obtain the sum and dividing this by three. In specialist terms: a triangular convolution is applied with kernel weights (1/4, 1/2, 1/4). An extra advantage aside from personal data protection is that it also eliminates to some extent the minor peaks occurring as a result of discretisation artefacts.