If a permanent redirect is supposed to transfer SEO from the old page to the new page, why has my domain authority been impacted?

[BlueLinkERP]

For example, we redirected our old domain to a new one (leaving no duplicate content on the old domain) and saw a 40% decrease in domain authority. Isn't a permanent redirect supposed to transfer link authority to the place it is redirecting to? Did I do something wrong?

[DanielFreedman]

I'd had good results doing page level redirects i.e. map each page on the old site to its closest corresponding counterpart on the new site.

Just coming up with the redirect map can take many, many hours of work. For a Subject Matter Expert, I had to read hundreds of articles on both the old and new sites.  Thankfully, I was interested in the subject!

[Thos003]

Link juice is lost in a redirect. You should never expect to gain 100% of link value from a redirect.

[BlueLinkERP]

No, we simply redirected all pages from the old domain to the new domain's homepage. We also got rid of some of the historic pages with links. That was probably what we did wrong.

[KristopherWho]

Dose the structure of the new sit mirror the old one? I am not very knowledgeable on the subject, but I am pretty sure the the new site needs to have the structure & page names as the old one. This way all the authority from each page can transfer to the new site.

[ORob]

A redirect transfers a good portion, but does not guarantee that all of that value will follow you to the new domain. I would suggest finding some of the highest value links to your old domain, contact the site owner, and have them update your info to the address of the new domain.