1. INTRODUCTION

2. OBSERVATIONS AND DATA REDUCTION  
2.1. The TOUGH Survey  
2.2. New Data and Their Reduction  

3. RESULTS  
3.1. GRB Host Luminosity Distribution  
3.2. The Evolution of the Median UV luminosity  
3.3. The UV Luminosity Function  

4. DISCUSSION  
4.1. The Impact of Hosts with Unknown Redshifts  
4.2. Influence of Selection Effects on Previous GRB Host Samples  
4.3. Origin of the Redshift Evolution of the Luminosity Function  

5. CONCLUSION