BIX - Der Bibliotheksindex

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Methodology of the BIX Index

The BIX results are calculated as follows:

1. BIX indicators are calculated for all libraries in Germany using German Library Statistics (DBS) data

All existing plausible data is used in the first step. This includes data for ca. 2.000 public and ca. 240 academic libraries. Data is available for 65 to 98% of those libraries. BIX for academic libraries uses four indicators that can not be computed from DBS data. The maximal peer group for these indicators are BIX-participants.

2. Percentiles are calculated for each indicator

Libraries are separated into their peer groups. All further steps refer to the peer groups.

The percentile is calculated for each indicator of each library.

The percentile describes the position of one library in relation to all libraries in its peer group. It is a number between 0 and 1. The library with the lowest value has the percentile "0". The library with the highest value has the percentile "1". All other libraries are in between these two. The library with a percentile of 0,5 is exactly in the middle of its peer group: 50% of all libraries have a lower value, 50% have a higher value. The 0,85 percentile means: 85% percent of all peer libraries have a lower value, 15% have a higher value.

The BIX-profile shows the percentiles of all indicators of the library as a diagramm.

Special indicators

As a rule, BIX rates indicator values as "the higher the better". There are some exceptions, however, in the target dimension efficiency (e.g. costs per visit). These indicators are rated in reverse order (lowest value is best value).

3. Indicators are aggregated to dimensions and rating groups are calculated

All percentile values of the indicators in one dimension are summed up and divided by the number of indicators in this dimension. The result is again divided into percentiles. They determine the final rating result of the library:

  • Top group (gold): a value in the upper third of all libraries (percentile over 0,66)
  • Middle group (light blue): a value in the middle third (percentile between 0,33 and 0,66)
  • Lower group (dark blue): a value in the lower third (percentile up to 0,32)

Due to this method, a single top- or bottom value cannot have an undue influence on the overall results of the library.

4. "BIX-TOPs" are computed

The rating group of the four dimensions determines the number of BIX-Tops ("stars") that the library gets.

  • One star is awarded for each dimension in the top group
  • Half a star is awarded for each dimension in the middle group
  • A maximum of 4 stars (for four ratings in the top group) can be achieved in total.
dbv - Deutscher Bibliotheksverband e.V.