How can I count a property list across all notes?

How can I count a property list across all daily notes, so that if I enter the same ListItem two days in a row it counts as 2, and if ListItem2 is listed only once that counts 1, listed like this, sorted by highest count.
ListItem - 2
Listitem2 - 1

Try:

```dataview
LIST count
WHERE Observations 
FLATTEN Observations as observation
GROUP BY observation
FLATTEN length(rows) as count
SORT count desc 
```

Query untested, but it should work…