How many terabytes per year would be created if Bitcoin replaced Western Union?

[minerva]

How many terabytes per year would be created in the block chain if Bitcoin replaced Western Union?

[anti-scam]

That's difficult to estimate. It's not simply a straightforward answer based on the transaction frequency, but also depends on what type of transactions are used, the transaction outputs created (or pruned) by each transaction, and other factors specific to Bitcoin.