ELO progression measured by year based on the games which were played that year. ELO numbers are based on the average rating of the 100 best engines and splitted into a (S)ingle (P)rocessor and (M)ulti (P)rocessor list, follow the orange links to view the details. Furthermore the statistic of the opening lines shows the quality of the randomness.
The massive ELO jumps in 2007 and 2010 are likely related to the echo of Fruit 2.1 and Strelka (hacked Rybka 1.0) in 2007 and the release of Ippolit (hacked Rybka 3) in 2009. The ELO jump in 2013 is probably related to the push of Stockfish.
First rating list appeared in 1984 in the dawn of availble chess programs mainly commercial dedicated units. A table of ELO progression by year can be found here but (unlike CCRL) is extremely influenced by all the different hardware that has been used during the years. Therefore to create ELO progression statistics from the SSDF rating list will be by hardware.
As far as I can remember the SSDF went online in 1996 and I have been able to reconstruct the rating lists they produced from 1996 till 2004, but missing the year 2005. You can download all of them in one 7z zip-file.
Only 2 hardware configurations are fit for a reasonable progress statistic by engine, the Pentium 90 and the Athlon 1200.