The number of unpaid contributions to the Linux kernel has fallen again since the last major update, as work on the open source operating system (OS) is increasingly borne by corporations.
The annual report from the Linux Foundation, which runs the project, showed that unaffiliated developers accounted for 12.4% of all patches during the fifteen months leading to December 2014, more than any single company.
However unpaid contributions fell to 11.8% of the total, having been as high as 14.6% just two years previously, which the foundation believes is yet more evidence that software developers are in high demand.
"There are many possible reasons for this decline, but, arguably, the most plausible of those is quite simple," the report said. "Kernel developers are in short supply, so anybody who demonstrates an ability to get code into the mainline tends not to have trouble finding job offers.
"Indeed, the bigger problem can be fending those offers off."
More than half of the updates to the Linux Kernel are handled by unaffiliated programmers and nine companies, including Intel which accounted for a tenth of changes on its own, as well as Red Hat, Samsung and IBM.
The report also noted that many of the top ten contributing companies were actively bringing in developers into the Linux community, with nearly half of the 4,000 developers contributing last year doing so for the first time.
"There are enough companies participating to fund the bulk of the development effort, even if many companies which could benefit from contributing to Linux have, thus far, chosen not to," the authors concluded.
"With the current expansion of Linux in the server, desktop, mobile and embedded markets, it’s reasonable to expect this number of contributing companies – and individual developers – will continue to increase."