I think there’s actually not 2 bars per year, but instead:
the first red bar = the year 2000
the second bar (which is not paired with another bar, and also, is not labelled at all) = the year 2002
the third bar = the year 2004
the fourth bar = the year 2006
and so on until the final bar, the twelfth one, = the year 2022
The x axis increases by 2 years each entry.
The number after the “|” is only meant to “helpfully” (and confusingly) tell you when those children were born. To take your example:
the data for the year 2000 is represented by the first red bar (7 per 1000 eight year olds had autism in 2000) and is labelled as 2000 | 1992 because those kids were born in 1992.
the data for the year 2008 is represented by the fifth red bar (11 per 1000 eight year olds had autism in 2008) and is labelled as 2008 | 2000 because those kids were born in 2000.
Any clue why there are 2 bars per year grouping?
I thought it was maybe number of cases in each year, but 2000 at the beginning of the graph and when 2000 appears later don’t match.
I think there’s actually not 2 bars per year, but instead:
The x axis increases by 2 years each entry.
The number after the “|” is only meant to “helpfully” (and confusingly) tell you when those children were born. To take your example:
That makes sense now! Thank you, I was having trouble wrapping my head around it!