How popular are the various flavours of HL7 v2.x?

Last year, HAPI's binaries were made available in the Maven central repo. An interesting side effect of that change is that the Nexus tool you use to upload new releases gives statistics about which binaries get downloaded. Since HAPI has an individual JAR for each version of HL7 2.x, this makes the Maven repository a kind of informal popularity contest for HL7 versions.

Obviously one would be foolish to use these numbers for anything, but they do give some interesting hints on the market penetration and adoption of various versions. Here is what they show:

Artifact	Downloads	DL%
hapi-structures-v25	2095	15%
hapi-structures-v24	1550	11%
hapi-structures-v231	1499	11%
hapi-structures-v23	1167	8%
hapi-structures-v26	1028	7%
hapi-structures-v251	903	6%
hapi-structures-v22	872	6%
hapi-structures-v21	762	5%

I'm kind of surprised to see 2.5 as the clear winner. My guess would have been 2.3 or 2.4.