Difference on average of y-axis between data sets

Question

How can I calculate in Mathematica the difference on average between the y-axis of two data sets such?:

data1={{0, 38.9583}, {100, 54.9419}, {33, 53.5451}, {10, 43.8448}, {45, 
  57.9104}, {88, 56.0035}, {69, 64.0202}}

data2={{0, 46.3}, {9.7868, 51.646}, {29.8381, 63.8548}, {49.8925, 
  70.7243}, {69.9485, 74.71}, {89.9136, 67.8673}, {100, 58.8}}

Manually I am getting that on average the y axis of data2 is about 8-9 bigger than data1 but I am not sure how to do it properly in Mathematica when the x values do not match exactly

Answer 1

data1 = {{0, 38.9583}, {100, 54.9419}, {33, 53.5451}, {10, 
     43.8448}, {45, 57.9104}, {88, 56.0035}, {69, 64.0202}} // Sort;

data2 = {{0, 46.3}, {9.7868, 51.646}, {29.8381, 63.8548}, {49.8925, 
     70.7243}, {69.9485, 74.71}, {89.9136, 67.8673}, {100, 58.8}} // 
   Sort;

EDIT: The value of the average difference will depend on the InterpolationOrder used in the Interpolation

Manipulate[
 Module[{f1, f2},
  f1 = Interpolation[data1, InterpolationOrder -> io];
  f2 = Interpolation[data2, InterpolationOrder -> io];
  avgDiff = (Integrate[f2[x], {x, 0, 100}] - 
      Integrate[f1[x], {x, 0, 100}])/100;
  Plot[{f2[x], f1[x]}, {x, 0, 100},
   Filling -> 1 -> {2},
   PlotLegends -> Placed[{"f2", "f1"}, {.2, .8}],
   Epilog -> {Text[StringForm["avgDiff = ``",
       avgDiff], {70, 45}],
     Red, AbsolutePointSize[4],
     Point[data1], Point[data2]}]],
 {{io, 3, "InterpolationOrder"}, 0, 5, 1,
  Appearance -> "Labeled"}]