Back in my early 737 days we used assumed temperature with paper charts. Later on we got computers which then allowed us to calculate assumed plus derate and thus on short flights allowing even greater reduction in thrust. I remember the first time I used this on a 4000 meter runway being asked by the tower if we had had an engine failure, the difference was that great! The calculation was correct and the tower got used to our high idle takeoffs. Personally I was very sceptical about what the local population thought of this improvement with us thundering over their heads much lower and our noise abatement then adding thrust. An earlier chief pilot in my opinion quite rightly disagreed with this but later on we would see increased thrust at a lot of places at 1000 feet.