The Pareto principle states that most effort / benefit (approximately 80%) is due to a limited number of key actions (approximately 20%).

             
Pareto chart analysis for b.vector
               Frequency  Cum.Freq. Percentage Cum.Percent.
  Delays       20.000000  20.000000  26.666667    26.666667
  Materials    18.000000  38.000000  24.000000    50.666667
  Customer     15.000000  53.000000  20.000000    70.666667
  Training      5.000000  58.000000   6.666667    77.333333
  Rework        4.000000  62.000000   5.333333    82.666667
  Errors        4.000000  66.000000   5.333333    88.000000
  Rain          3.000000  69.000000   4.000000    92.000000
  Wind          2.000000  71.000000   2.666667    94.666667
  Permissions   2.000000  73.000000   2.666667    97.333333
  Inadequate    1.000000  74.000000   1.333333    98.666667
  Temperature   1.000000  75.000000   1.333333   100.000000