Everyone on this thread overestimates the effects of drafting drastically, especially in these huge stadiums where the wind is negligible. 1 second max over 1500m at this level. Wanyonyi soloed a 1:41.70 following a heat at the Kenyan trials and was only able to go around a tenth faster with pacers in Paris a few days later. Countless other examples of people running PBs/extremely close to them from the front.