Bugs Per Line Of Code
Bugs / LOC is only relative to an individual. For businesses that implement bug tracking tools that link with their source code repository. It's possible for a manager to organize issues by developer, sorted by past issues and code changes.
Bugs Are Relative To Your Job
A senior software developer, who is highly experienced, highly skilled, very smart and able to take on independent jobs is far more likely to have way more bugs logged in a tracking system, then a junior developer with little experience.
How is that possible?
Senior developers are often engaged in higher risk development tasks. Refactoring of code and building new systems as an example. Junior developers are often assigned to fix known issues that aren't worth the time of a senior developer.
Therefore, by task assignment a junior isn't introducing bugs but fixing them, and a senior developer is allowed the risk of introducing them, because the benefit of what they are trying to archive is more important then the minor issues that are raised completing those tasks.
Language Syntax Is Important
The argument that a language introduces less bugs, because it can achieve more in fewer lines of code is a complete myth. Highly structured languages like C++/C#/Java force the developer to clearly express in writing what the desired instruction should be, where as languages like Python/PHP are very unstructured. Those languages allow for written expressions that not only will confuse a developer, but also the language parser.
The Compiler Reduces Bugs
How many bugs in Python/PHP have made it out into production servers, because there was no compiler to warn the developer that something was incorrect. When you measure bugs per LOC is that before or after a compiler has processed the source code?
Idiots Per Language
People program software at all different levels, from beginner to advance and there are programming languages for each of those. While developers will argue until their blue in the face about which language is better. There is no questioning the fact, that some languages attract more idiots then others. Some people learn Java, because they simply want to earn more money (not for any reason based upon the features of the language).
So if you would like to select a programming language, with the hopes of seeing fewer bugs, then select the language that has a smaller population of idiots in it. You'll be less likely to hire them later when the project has grown.