function (key, values, rereduce) {
  // value -> [count, min, max, mean]
  var i = 0
    , l = values.length
    , min = values[i][2] // set min to the first max
    , max = 0
    , mean = 0
    , count = 0
  ;

  for (; i < l; i++) {
    min = Math.min(min, values[i][1]);
    max = Math.max(max, values[i][2]);
    mean = ((mean * count) + (values[i][3] * values[i][0])) / (count + values[i][0]);
    count = count + values[i][0];
  }

  return [min, max, mean];
}