title: Benefits of panda's multiindex?
body: <p>So I learned that I can use DataFrame.groupby without having a MultiIndex to do subsampling/cross-sections.</p>
  
  <p>On the other hand, when I have a MultiIndex on a DataFrame, I still need to use DataFrame.groupby to do sub-sampling/cross-sections.</p>
  
  <p>So what is a MultiIndex good for apart from the quite helpful and pretty display of the hierarchies when printing?</p>