The text for stock market indicates:
"a stock market will significantly increase morale"
which seems odd...

Going inside the xml files, I indeed saw that a stock market did improve economics+15 AND morale+10 AND some other+5.

The text is misleading (the major effect is forgotten to the benefit of a less important effect) and incomplete (I had to go inside the xml file to discover the whole story).

I suspect that this may also be true with a lot of other building (although I did not verify this statement).