There a black joke amongst doctors in the UK where all the junior doctors start in the same week each year the mortality rates go up :-)
Sources :
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2896592/ https://www.ncbi.nlm.nih.gov/pubmed/21747093
Or of course it means, that attending doctors do a constant amount of (insufficient) supervision, or they ramp up supervision after someone screws up... :|