Why do we not know how many people died because of the British blockade of Germany in World War I?
Short answerWe do have several estimates, and Steve R. Dunn's Blockade provides a useful treatment of them.
NotesHistorians have several estimates for deaths caused by the blockade of Germany. The problem is evaluating their ranges and methods rather than facing a total absence of evidence. Steve R. Dunn's Blockade is recommended for a fuller treatment. Disagreement among estimates should not be confused with having no historical knowledge at all.