I do know that sometimes graphs with weird dog-legs are caused by either graphing the wrong derivative[1], or because there are more populations and someone is either being devious or is unaware.

[1] Developers are by and large flummoxed by S-curves for progress. An S curve for distance maps to a bell curve for velocity. If the sums don't make sense, look at the rates, or the rate of change. Don't keep staring at the S trying to fit trend lines.