Page Fragment rendering order (with plugins)

I have a few plugins that use page fragments that insert into the same insertion point.
Each of these plugins inserts html into the insertion point, one right after the other. I'm wondering how the order in which those plugins are rendered is determined.

Assuming the page fragment file name is in the following format:
{PAGE_NAME}.{UNIQUE_STRING}.{INSERTION}.{POINT}.txt.

I've found that when in the CPM page, the page fragment filenames have the UNIQUE_STRING portion of the filename replaced with plugin Name provided in the plugin.xml file. I thought that maybe the plugins were ordered according to the plugin Name alphabetically, but this isn't the case.

I also thought that it may be the order in which plugins are installed or activated that determines the order in which the page fragments are rendered, but this is also not the case.

Thanks for any help and information you can provide.