This document presents a study on software population pyramids, which graphically represent the distribution of contributors to open source software projects over time. The study analyzed activity data from 90 open source projects on GitHub. It identified four common shapes of software population pyramids and showed how the pyramids for two projects, homebrew and blueprint-css, evolved over multiple time periods. The software pyramids provide insights into the current status and future sustainability of open source development communities.

1. Software Population Pyramids:
The Current and the Future of OSS Development
Communities
Saya Onoue, Hideaki Hata, Kenichi Matsumoto
Nara Institute of Science and Technology, Japan

2. (General) Population Pyramids
2010 Italy
http://populationpyramid.net/ 2

3. (General) Population Pyramids
u We can understand the
current status of the
country.
u They are useful to predict
the future.
3
2010 India
2050 Italy
http://populationpyramid.net/
This form is common in
developing countries.
This form is common in
low birth rate and
longevity countries.

4. Software Population Pyramid?
4
homebrew 2013

5. Software Population Pyramids
u They represent a distribution of contributors
to perform coding and discussion.
• Discussion contributors: developers contribute to comments and/or
issues.
• Coding contributors: developers contribute to commits and/or pull
requests.
• Moved contributors: developers have started coding contributions
after discussion contributions
5

6. Dataset
u We analyze the GitHub dataset provided by
Gousios*.
u This dataset includes developers' activity
histories of 90 OSS projects.
*G. Gousios. The ghtorent dataset and tool suite. In Proc. of MSR '13, pp. 233-236, 2013. 6

7. How to make a Software Population
Pyramid
period
0
number of contributors
7
Software population pyramid in t1
Δt4
Δt3
Δt2
Δt1
contributor 1
t1
initc lastc
coding
less than Δt1

8. How to make a Software Population
Pyramid
8
period
0
number of contributors
initd lastd t2
Δt4
Δt3
Δt2
discussion
initc lastc
less than Δt1
Δt1
coding
contributor 2
Software population pyramid in t2
t１

9. Research Questions
1. Are there any types of software population
pyramid in shape?
2. How do software population pyramids
change over time?
9

10. 10
1. Types of
Software Population Pyramids
Type A
Type B
Type C
Type D

11. 11
paperclip 2011/12
Many discussion contributors,
but less coding contributors.
Type B

12. 12
clojure 2011/12
Type C
There is no moved contributors

13. Evolution of homebrew
u homebrew
13
2010/06

14. Evolution of homebrew
u homebrew
14
22001101/06

15. Evolution of homebrew
u homebrew
15
220011021/06

16. Evolution of homebrew
u homebrew
16
2200110231/06

17. u blueprint-css
17
Evolution of Blueprint-css
2010/06

18. u blueprint-css
18
Evolution of Blueprint-css
22001101/06

19. u blueprint-css
19
Evolution of Blueprint-css
220011021/06

20. u blueprint-css
20
Evolution of Blueprint-css
2200110231/06

21. 21
Evolution of
Software Population Pyramids
homebrew
blueprint-css

22. Conclusion
u We propose software population pyramids, graphical
illustration of OSS communities.
• We distinguish coders from not coding contributors.
u The shapes of software population pyramids vary
depending on the current status of development
communities.
• We found 4 types of the shapes.
u Monitoring and maintaining software population
pyramids can be useful to succeed in sustainable
OSS communities.
22