There's a recent talk  by Mary Shaw from Carnegie-Mellon University (CMU). It's about what has happened since the NATO conference in 1968 (dubbed the Software Crisis), and what engineering means in software engineering.
According to their survey, the American workplace consists of ~90 million "casual" programmers, and ~2.5 million highly trained software engineers, and there's a need to get more programmers into the engineering aspects.
 Progress Toward an Engineering Discipline of Software:
There's a link to the slides in the description of the video.
I don't believe that statistic for a second, unless we're using some convoluted definition of "programmers" which includes anyone who can open Microsoft Word.
That would mean half the labor force can program. Ludicrous.
Looking at the slides, I'm pretty sure you interpreted that wrong. There are 90M end users of software, not 90M "casual" programmers.
Please see the relevant part at 49:50 , but I'll bring it in next.
The speaker pretty much defines "end users"/casual developers as people who do programming like things; "There are something like 90M people out there who are doing 'programming like things'; they are building databases, they are building spreadsheets, they are using scripting languages, they are building sophisticated websites--what are we doing to help them?"
It's a broad category, but I think the confusion is that programming is not simply about writing code, it also includes the overall architecture, and design of a system.
So what I get from this is that end users means anyone who didn't go through the academic channels to learn the engineering aspects, and that's who they need to reach. The speaker had a link to their software engineering programs at CMU  in an earlier slide.
Also, see the context in view of the stackoverlow survey--which doesn't add up if you look at the numbers, but the speaker explains it's because some people reported in more than once.--It sought to be an example of how "end users" end up doing "programming like things."
 Progress Toward an Engineering Discipline of Software
 Software Engineering Masters Programs