1. Introduction  
2. Selection of the data samples  
2.1. The Sloan sample  
2.2. The Spectroscopic sample  
2.3. Accuracy of the samples  
3. Global distribution of spectral slopes  
3.1. Comparisons between the samples  
3.3. Global analysis of the Spectroscopic sample  
3.4. Discussion  
4. Distribution of spectral slopes for selected asteroid families  
4.1. Families in the L4 swarm  
4.2. Families in the L5 swarm  
4.3. Discussion  
5. Conclusions