A linear scale for that graph is completely appropriate: it’s showing how one data series has flattened out and the other continues to grow at an increasing rat

A linear scale for that graph is completely appropriate: it’s showing how one data series has flattened out and the other continues to grow at an increasing rate. I would also argue that since one of those data series is clearly not exponential (it’s more of a sideways S-shape) it would be harder to interpret what that series actually looked like on a log scale. If you choose to plot things on a logarithmic scale, you open a whole can of worms with expecting your target audience to be educated numerically and understand the implications of a line on a log-scale (which looks far less dire than an exponential on a linear scale).