It's interesting here that 1943 fighter losses were much lower than 1944, despite an apparent completed switch (in 1943) to mostly Spitfire activity judging from the distribution of losses.
The John Foreman figures are as noted Fighter Command/ADGB/2nd TAF ONLY, as a result most of the reported conclusions are invalid
To me this indicates the later models of the Spitfire did not improve survivability despite a declining Luftwaffe. Or that the later models took a lot of ground attack losses.
To me this indicates a lack of awareness of sortie rates. Day operations, in 1942 Fighter Command reported 91,772 defensive and 43,003 offensive sorties, in the first 4 months of 1945 Fighter Command and 2nd TAF reported 11,375 defensive and 75,565 offensive sorties, multiply the 1945 figures by 3 to give an idea on tempo and it would give around 230,000 offensive sorties for 12 months, or about 5 times the 1942 rate, not surprising losses were greater per month but lower per sortie. Then factor in 1942 there were few fighter bomber sorties as a percentage of total sorties compared to 1945, so the 1945 operations had much more flak exposure.
The way they are probaby wrong is that a lot of axis air to air kills are counted as flak kills or unknown, or accidents. Also, a huge amount of Allied air to air kills are likely vaporware. The same applies to some dubious Axis claims,
Given these claimed adjustments (add "lot" more, subtract "some") do Luftwaffe fighter claims head toward 1 claim to 1 shoot down? While allied claims subtract "huge amount" go below 2 claims to 1 shot down or more? Please present the numbers you must have to make the above statements. The above hand waving adjustments explains how the turn fighter idea was created.
After all the current conclusions are Luftwaffe fighters over claimed maybe 3 to 1 or even more in the Battle of Britain, looking at the 8th Air Force B-17 losses the Luftwaffe fighters remarkably consistently, month after month, claimed around 2 B-17 shot down for every one reported lost to fighters, for B-24 the monthly figures move around more but end up at about 1.8 to 1. And so on. There are a number of works cross checking losses and claims and generally make it clear everybody over claimed on average, with most claims made in good faith.
Minor examples, ZG1 claimed 8 kills in the two big fights over U-255 (plus 4 minesweepers and a Sperrbrecher) on 11 April 1944, in the first fight 3 Mosquitoes failed to return, and 1 was written off but 2 of the Mosquito losses were to flak and another was hit by flak before being finished off by a Ju88. The second fight later that day saw 1 Mosquito lost and another written off. Some 7 Ju88 failed to return that day. The RAF claimed 6 kills.
On 18 February 1944, the Amiens Raid, the RAF lost 1 Mosquito to fighters and 1 to flak, JG26 claimed 2 or 3 kills.
On 1 December 1943 ZG1 claimed 2 Mosquitoes while losing 3 Ju88, the RAF lost 1 Mosquito and claimed 2 kills.
On 13 June 1943 JG2 bounced a Mosquito fighter formation, claimed 3 and shot down 3.
As to the P-51 vs P-47 debate, one set of data I memorised from another French article was that the P-47 scored 140 of 220 Big Week kills, the P-38 and P-51 sharing 80 in an unknown ratio. ... During Big Week, with 1/5 the sorties, the -51B destroyed 64.5, the P-47 destroyed 78. The P-38 destroyed 10. (This totals 152.5, a long way from 220)
Mighty Eighth War Diary, it does not break down claims by type for 20 February 1944, for 21, 22, 24 and 25 February the totals are P-38 279 sorties despatched, 3 claims, P-47 2,373 sorties despatched, 102 claims, 352 sorties despatched, 51 claims, P-38 1 claim per 93 sorties, P-47 1 claim per 23.3 sorties, P-51 1 claim per 6.9 sorties. On 20 February, 94 P-38, 668 P-47 and 73 P-51 sorties made 61 claims between them, giving 217 claims for the 5 days, 373 P-38, 3,061 P-47 and 425 P-51 sorties despatched, total 3,859.
The Luftwaffe quartermaster thinks Luftflotte Reich and 3 lost around 240 day fighters MIA and in air combat to allied aircraft, including the 15th Air Force.