The Danish occupation-to-qualifications mapping based on what amounts to a JA approach maps all major occupational groups (DISCO codes at the one-digit level) to just four different qualification requirement levels.<sup>17</sup> Similar mappings for other countries are somewhat richer in detail. For the Netherlands, for example, van der Meer (2002) describes a mapping into seven different qualification levels. Moreover, there are difficulties in translating job requirements into years of schooling (a key variable in the econometric analysis below) because not all jobs require very much formal schooling, but may be characterized by more on-the-job training. Also, different educations that are equally appropriate for a given type of job (with a given qualification-level requirement) are characterized by very different lengths of schooling (measured in years), which makes it difficult to create relevant limits. Finally, such classifications are rapidly outdated. In the case of Denmark, this classification makes use of a mapping between DISCO-88 and ISCED-76<sup>18</sup> classifications and Statistics Denmark is only now in the process of updating this to the DISCO-08 and ISCED-97 classifications. For all these reasons, the JA approach is not very attractive for the case of Denmark.

The WA approach uses surveys to ask workers how much education or schooling is required to perform (or obtain) their particular job. These responses are then used to compare the level of education workers _believe_ is required to perform (or obtain) their job with their actual education level. On the positive side, this method is up-to-date and specific to each individual’s job. On the negative side, this is a highly subjective measure, and it is commonly known that individuals have a tendency to inflate reported educational requirements. They may also simply be restating actual hiring practices or at least what they believe to be so. Furthermore, there may be systematic biases in how job requirements are assessed across genders and other groupings.<sup>19</sup> In any case, subjective survey-based information on job-to-education mismatch in an individual’s current or previous job, overall job satisfaction and other relevant issues is not available for this current study.<sup>20</sup> The RM approach derives the “adequate” education level as the mean or median (and sometimes the modal value) of the observed distribution of actual educational attainment (measured in years of schooling) in each occupational category. As such, it measures the outcome of the actual matching process (the interplay between labor demand and supply) as determined by current hiring standards and labor market conditions. For this reason the RM measure must be interpreted differently from the WA and the JA measures.<sup>21</sup> An individual is then taken to be overeducated if his actual level of schooling is greater than the norm, or reference, level of education in his occupational category (with undereducation similarly defined). Several authors

> 17 The four levels of qualification requirements are those used in Tables 3-8, i.e. elementary, low, medium and high. 18 ISCED: International Standard Classification of Education.

> 19 Based on survey information, Chevalier (2003) and Chevalier and Lindley (2006) distinguish between apparent overeducation and genuine overeducation, by asking respondents to comment on their satisfaction with the match between their education and their job. They assume that formally overeducated employees are only apparently overeducated if they are satisfied with this match, whilst formally overeducated employees are genuinely overeducated if they are dissatisfied with the match.

> 20 Analysing the case of Sweden, Böhlmark (2003) finds that overeducation is associated with lower job satisfaction. Also, he finds that workers who improve their education-to-job match over time become more satisfied with their jobs.

21 Verhaest and Omey (2004) argue that the RM approach is an appropriate estimate of the privately optimal level of education only if labour markets are flexible and efficient. Otherwise, the RM measure may systematically either over- or underestimate the complexity level of jobs.

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