Upon further inspection, although a shift of 4 (on a 64-bit linux box)
isn't perfect for dict, it's fairly close to it and well beyond random
hash values.  Mixing things more is just gonna lower it towards random
values.

>>> c()
  2:   1,   1,   1,   2,   2,   1,   1,   1,   1,   1,   2
  4:   1,   1,   2,   3,   4,   3,   3,   2,   2,   2,   3
  8:   1,   2,   4,   7,   8,   7,   5,   6,   7,   5,   5
 16:   2,   4,   7,  11,  16,  15,  12,  14,  15,   9,   7
 32:   3,   5,  10,  18,  31,  30,  30,  30,  31,  20,  12
 64:   8,  14,  23,  36,  47,  54,  59,  59,  61,  37,  21
128:  16,  32,  58,  83, 118, 100, 110, 114, 126,  73,  41
256:  32,  64, 128, 195, 227, 197, 203, 240, 253, 150,  78