Simple graphical reporting

I have written a few posts in the past on the use of infographs to get a key message or statistics across to managers. While on holiday in Germany,  I visited a now disused mine and I came across this:

It is a simple graph which shows the injuries at the mine for a nine month period. It does not need much explaining. What strikes me is its utter simplicity – it gets the number across in a clear and simple manner. It should be understood by all staff from managers to workers. It’s on a single page, and drawn manually – probably pre-dates computers.