k  inertia (lower = tighter groups)
2 225.6
3 67.3
4 44.7
5 36.7
6 29.3

       shoppers  avg_spend  avg_visits
group                                 
1           147     8320.0         6.0
0            88    30261.0        21.0
2            65    70935.0        12.0

Saved shoppers_grouped.csv