The graph in the OP doesn't seem to match the numbers to me. The red and green losses peak at about the same level. Red spends about a month near that peak, so they're certainly losing more during Bloody April (or whatever month that was), but it doesn't look like there's five times the area under the red curve than the green one. I'm not sure I trust the presentation of the data. (Are the numbers supposed to be the current day/month/year? Most recent full month? A rolling 4-week window, or calendar month to date? Is the total shown over the whole period of the graph, or just the most recent interval?)
One of Secret Master's old tests put the extra loss ratio from a 2:1 numbers disadvantage, everything else being equal, at about 1:1.5 (so not even quite equal to the enemy advantage). It's an important factor, but there's something else involved.
What were the accident losses? (And do you know those of the enemy, as opposed to air combat kills -- or kill claims)?