This graph seems to offer a point against my claim that progress has been recently accelerating (while totally confirming my claim that billswift is making stuff up), so I'll explain.

The late 90s drop you can see on the graph is a statistical artifact related to AIDS, early 2000s cutoff, and clustering countries into unnatural categories.

The worst affected countries were mostly in relatively well off countries like South Africa, Botswana, Namibia, Zimbabwe (it was well off until recently) etc. that don't really cluster with most of the poor Sub-Saharan Africa, and have incomes and standards of living more like Brazil or Turkey. Most of them had clear and very rapid rebounds in life expectancy since the worst in early 2000s in any case, trend-line won't be significantly affected by that.

For the poor everyone else of Sub-Saharan Africa, AIDS had much less severe effects, and for many like Nigeria I mentioned you wouldn't even notice anything just looking at life expectancy statistics. Here's per-country graphs going to 2008.

Disregarding AIDS, the most recent decade has been the best one ever for Africa by nearly any metric, be it average income, equality, poverty rates, democracy, peace, etc.