Here's this shows TL;DR:

• A return does not equal a refund
• There are multiple types of return outcomes 
  • A variant exchange 
  • A different product exchange 
  • Store credit 
  • A refund 
• Most shoppers want an exchange and that extends the shopping relationship 
• You focus so much on frictionless acquisition what about frictionless retention?
• Your goal should be drive refunds down and exchanges up 
• Tips that we see top Shopify brands use to drive more exchanges

Other helpful resources on this topic:

How to build a customer centric return policy (ebook)
The different types of returns and how they impact LTV