When taking only the three green components (education, work experience, and management tasks) into account, the statistical model can explain about half of the variation in the individual wage rates observed in 2019 in the Danish public sector (Lønstrukturkomitéen, 2023d). The implication is that the other half must be explained by other factors, for example, those suggested in the blue circles.
Higher values of the three green components are (on average) positively associated with the hourly wage rate. Based on economic theory (see Mincer, 1974, and Becker, 1964), this positive relation is expected, it is supported by the statistical model, and, as seen in figures 3.1 and 3.2, it also holds true in practice, even when just plotting raw values for education, experience and hourly wages.
For some occupational groups, factors other than education, work experience, or management tasks might be more (or less) important for the wage rate, for example, some of the factors suggested in the blue circles in Figure 3.3. These other factors could easily move hourly wages in opposite directions and thus, when combined, seem not to be important for determining the wage rate. Therefore, it makes sense to analyse these ‘other factors’ to try to identify potential patterns concealed by the results of the model. For example, if certain occupational groups do a wide range of many different tasks, have different levels of responsibility, or include individuals with systematically different (un)observed characteristics, it will be difficult for the statistical model to accurately predict the actual hourly wage rates.
More formally, when interpreting the outcome of the statistical model, we therefore also investigate how large a part of the observed hourly wage rate cannot be directly associated with education groups, work experience, and management tasks, as this gives us information about the importance of ‘other factors’. For the 50 occupational groups, Figure 3.4 shows how large a portion of the wage rate is not explained by either education, work experience, or management tasks (the unexplained part is formally called ‘the residual’), and it captures the deviation between the actual observed wage rate and the predicted wage rate from the statistical model. The deviations are depicted as a percentage of the average wage rate for each occupational group, and the equivalent value in DKK is specified for a few groups. Deviations between actual and predicted wages for a specific occupational group can be down to either the ‘other factors’ or the fact that the return to wages of education, experience or management tasks for the specific occupation differs from the average.
If the residuals are positive, it means that the sum of the other factors contributes to a higher wage rate for the particular occupation than the statistical model predicts based on education, experience and management tasks. If, on the other hand, the residuals are negative, it implies that, for the particular occupation, the residuals contribute to a lower wage rate. It is important to note that the deviations across all occupational groups sum to zero in total and are thus measured in relation to averages for the whole model and should not be interpreted as absolute values.
It is also important to note that predicted wages do not (necessarily) reflect productivity and, importantly, that predicted wages cannot be interpreted as ‘fair’ or correct wages. The predicted wages solely describe the average return of education, experience and management tasks for the occupation and how these factors are rewarded under collective agreements.
The statistical analysis shows major deviations between predicted and actual hourly wages for the occupational groups that have the lowest absolute wages on average. Particularly for occupations such as cleaning assistants or different types of childcare or elderly care assistant jobs, the observed average hourly wages are lower than the model predicts. An important reason for the model overshooting the expected hourly wage is that little or no education or training is required to fulfil the formal qualifications for these occupations. As such, some people in these occupations have more education and training than formally required, for example, if they have taken a formal education and later changed their career path. In such cases, the statistical model includes the (high) educational inputs from the completed formal education and predicts that they are not paid according to their educational qualifications. However, in practice, they might be paid according to their qualifications and productivity in terms of the actual tasks they perform, and the statistical model does not account for that when it only includes a measure of the highest completed level of education.
The occupational groups for which the statistical model more often predicts that individuals are paid more than their educational qualifications, work experience and management tasks suggest include engineers, doctors, teachers, and police officers. For some of these groups, there could be hidden (from the model) qualifications, e.g. when supplemental education or training is not registered as an increase in the highest completed level of education. Thus, the wages for a given education group could be artificially high, as is the case with police officers, for example. However, having a higher actual wage rate than statistically predicted could also be a sign of particularly demanding or dangerous tasks or ones requiring a high level of responsibility. The statistical model does not observe such job characteristics, and they would, therefore, be categorised as unexplained reasons for higher (or lower) observed wages. However, the observed differences could also merely be driven by unpaid overtime, which is not captured by the standardised hourly wage rate.