Unless the purpose of the chart is to convey the message that the subject under analysis is very complex, I think such a chart serves no real purpose.
To make a chart which can give insight to humans, I would consider an approach based on summarising the flows, perhaps a clustering approach. you could then have a few simple, bold flows, and add some text / a key to categorise the flows .
Consider the examples here:
in the first, there is a natural heirarchy at the level of continent. Imagine if the chart was at the level of postal/zip code, it would become unreadable.