Nowadays whenever you use Maven, Gradle or some other Java build tool when you download some artifact (Java library), you probably download it from Central Repository (it may be through JCenter, your company's Nexus, Artifactory or some other proxy / repository, but ultimately it's usually downloaded from Central Repository). Central Repository (also known as Maven Central Repository) is sponsored by Sonatype (company founded by Jason van Zyl, Apache Maven founder).

In this article I will use two terms: GAV (groupId:artifactId:version - for example 'junit:junit:4.12') - basically it's a "project's version" and GA (groupId:artifactId - for example 'junit:junit') - basically it's a "project".

So how many artifacts are in Central Repository (as of 01.01.2017)?

This chart shows cumulative sum of all GAVs:

This chart shows cumulative sum of all GAs:

This is annual growth (GAVs):

As you can see, in last few years it has been steady 40% annual increase, even though Central is almost 10 years old!

Let's see these numbers inside the chart (blue line shows number of new artifacts (GAVs) added every year, black line is their cumulative sum):

And the same for GAs:

So far everything is peachy. Last chart is a little bit more difficult to explain and interpret. I guess it could be labeled as ("age of projects (GAs)"). For every project I computed how old was it's last artifact's version (GAV) at the end of every year. Currently (stats for 2016) there are over 47% of projects which were updated within last 12 months. Maybe a little bit alarming is a fact that about 37% of all projects were not updated within last two years ... maybe because they were abandoned by their creators or maybe they are stable enough so that they don't need an update? Who knows?

You can always check latest progress on javalibs