Trends in waiting time to date and total time waited: are the sources compatible?

Department of Health Waiting List returns routinely measure the number of patients waiting for elective NHS admitted patient care on a given day, grouped by long they have been waiting to date. The trend in the average waiting time estimated from this istribution is different from the trend in the average total time waited by patients admitted over a period of time, calculated from Hospital Episodes Statistics. This article investigates whether the results from the two sources are consistent.