This chart from Reuters is making the rounds on Twitter today.
Quickly, tell me whether the Gun Law in Florida did well or poorly.
That of course is the entire purpose of the chart.
This is the double edge of novelty in charts. There should be a very high bar against running counter to convention. Readers do bring their "baggage" to the chart, and the designer should take that into consideration.
Some commentators are complaining about trickery. That may be true. But it's also possible the designer actually thought reversing the direction of the vertical axis made the chart better.
Don't forget about we have another convention: up is good and down is bad. Fewer murders is good and more murders is bad. So why not make it such that a rising line indicates goodness (fewer murders)?
Going back to the Trifecta Checkup. This chart has dual problems. We just talked about the syncing between the data and the graphical element.
The other issue is that the data is insufficient to draw conclusions about the underlying question: what explains the shift in number of murders since the late 2000s? This is a complex problem--the chapter in Freakonomics about abortion and crime rate is still instructive, not for the disputed conclusion but for the process of testing various hypotheses. The reduction of the complex causal structure to a single factor is dissatisfying.