A few years ago Bristol City Council released a dataset containing the results of an annual survey of abandoned shopping trolleys in Bristol rivers from 2005 to 2011. This is one of those datasets that turns up in lists of “quirky” datasets.
The chart is an isotype chart, which is basically a barchart made up of icons to make it more visually appealing. In “Fundamentals of Data Visualization”, Claus Wilke suggests that you “make your figures memorable”, and the isotype chart is one way of doing that.
Visualization type: isotype chart, pictogram
Data source: Bristol City Council, archived by The National Archives, CSV, 1.2 KB