Gripen,
The higher concentration of fighters in the German raids reduced the edge that Fighter Command had previously enjoyed: the Germans could afford to trade Me109s, one for one, with Spitfires and Hurricanes!"
Don't know how else to interpret this for you. It's pretty cut and dry. The LW could afford the lose ratio as long as they kept to the "Airfeld" strategy.
"Production of the Me109 (190 per month) was about one-half the British production rate for the Spitfire and Hurricane. Reserves were sufficient to keep most fighter units at 80 percent strength and bombers at 86 percent."
You've conviently taken this out of context and changed the authors meaning. What this statement says in fact is that the LW was not straining it's production capacity to keep it's units at full strength. Yes, ask any Military Intelligence Anaylsist, 80 percent is considered a combat effective unit.
Regarding the change on fighter strategy, please check again USAAF statistical digest. There is not too many enemy fighters claimed in ground by USAAF fighters before April 1944 (assuming that Doolittle's strategy means also attacks against air bases).
The LW "Airfield" strategy and Doolittles change to the USAAF strategy are the same. The fighters were freed to go and destroy the Enemy WHEREVER they were found. They were not tied to visual distance escort of bombers nor did they have any restrictions on them once contact was made. Their orders were the same....DESTROY THE ENEMY. Chase him down and kill him. Leave him no safe haven.
In the case of the LW, Goering took a successful strategy and began to unravel it by placing restrictions on the fighters (visual range escort) AND he completely changed the targets. Both gave the RAF a "safe haven". Fly beyond visual range of the bombers and the 109's would disengage. Then you could reattack or land safely at your field....refit and do it again.
Before Doolittle came along the LW fighters had their own "safe havens". The Allies had an altitude restriction and couldn't chase below it. So LW fighters could dive for the deck and live to fight again. The Allied fighters were tied to close escort of the bombers leaving the airspace around them free for LW fighters to use unmolested. The LW could take off, form up, and attack at their leisure. Doolittle did the exact opposite of Goering. He denied the LW safe haven.
Once that safe haven was removed and the full wieght of a numerically/tactically superior enemy could be brought to bear, it did not take long to push either Air Force to the brink of destruction. In '44 the LW went over the edge and ceased to exist as an effective fighting force. In '41 the RAF was pushed right to that edge.
Crumpp