Two years ago I produced some statistics on addresses in OSM. While I did regularly re-run the scripts, I never really revisted the topic to see how things are developing,
2013-03-27 2015-04-09 Increase since March 2013 Total 20'168'470 51'903'310 257% Germany 3'659'043 8'470'716 232% USA 2'090'893 5'229'243 250%
The complete set of numbers can be found [here] (http://qa.poole.ch/addresses/), According to official statistics there are 18.5 million residential buildings in Germany so I would expect that we are roughly 1/3 to 1/2 of the way to complete coverage there.
The large global increase in early 2014 is mainly due to the import of 8.7 million addresses in the Netherlands which due to peculiarities in building and numbering in NL led to a far larger increase in the counts than you would normally expect of a country with a similar population size.
When I first produced the address stats the openaddresses.io project didn’t exist and it it is now interesting to compare the two projects. It should be noted at this point that openaddresses.io does not make any representations wrt licences of their individual datasets and there is no guarantee that all or any of the data could actually be used in OSM.
OA currently claims to contain 115 million address, slightly more than twice the 52 million in OSM. However how large is the overlap? A very rough (and unfair) estimate based on the numbers for the US, ES, NL, PL, DK, NO and JP in OSM, would indicate that 24 million address likely turn up in both projects, but, more interesting that OSM contains 28 million addresses not in OA. Or put differently a combined dataset would contain 143 million addresses (see caveat above).