"Z  ....Pairs"

00 01 02 03 04 05 06 07 08 09

11 12 13 14 15 16 17 18 19

22 23 24 25 26 27 28 29

33 34 35 36 37 38 39

44 45 46 47 48 49

55 56 57 58 59

66 67 68 69

77 78 79

88 89

99

 Pairs fall at the rate of 3 per day when Singles or (non double) numbers hit each day.  Single numbers hit around 263 days per year on average.

 263 x 3 = 789 regular pairs per year for Single numbers

 On the 99 to 102 remaining days of the year that doubles hit only one regular pair falls per day.

                    789 +99 = 888 regular pairs per year fall on average.

                  About 987 pairs fall per year....Regular and Doubles

      Sooooo ....  of the 45 regular pairs we can expect each one of those to hit an average of 19.73 times each per year. 

                                   Regular pairs  19.73 each per year

                                    Doubles pairs   9.9  each per year