# Difference on average of y-axis between data sets

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

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"}]