When looking closely at some set arithmetic, I realized that all of the three symbols in the following minimum example are rendered here (pdfLaTeX on Portable MiKTeX, Windows 7 x64) at different vertical positions:

```
\documentclass{article}
\begin{document}
$x \in X$
\end{document}

```

Magnified screenshot, when viewed in Adobe Acrobat Pro 9 (added red line manually):

![$x \in X$](https://i.stack.imgur.com/LWPJy.png)

**The question:** (why) is this as it should be? My naive view would expect at least `$x$` and `$X$` to share the same baseline.