Take a look at these images from Jornal Nacional, the main TV news program in Brazil. Two nights ago, they announced the US$/BRL rate had dropped. They used a line chart. The angle of the line is big. Major drop? No. It was a 0,05% drop (from 1,723 to 1,722).
Then last night, it was up. A much bigger difference, at +0,34%. The line chart? It is there. The angle of the line? The same.
Conclusion? It is not a line chart. It indicates just a binary information: if the rate is up or down. Isn’t the up/down arrow already doing exactly that? So why use a line-graphic-like image, that implies the idea of “angle=quantity of change”?
Earlier in the week: