I would try viewing the document using the PAC 1.3 "Preview" feature. It displays the table in the way that an AT user would hear it, and allows for checking the association of header and data cells. It is free, you can find it here Downloading PAC 2 - Stiftung «Zugang für alle» - scroll to the bottom of the page under "Older Version". Grab PAC 2 while you are at it - it is much more thorough that the Acrobat Pro checker, but PAC 1.3 has a better preview feature when working with tables.
Something else to think about - as you point out even a correctly-tagged complex table can be problematic for AT. Sometimes I will tag a table like yours as a simple, regular table in spite of the visual representation. Using Span tags with alt text, change "Dollars" to "GDP: Dollars", "Euros" to "GDP: Euros" and so on.
As far as tagging a complex table as simple with the exact method you're saying, you are too smart. I'd discussed that on another forum, and our company tried it. Worked fine, but the client would not accept it.
Anyway, here's the table in PAC 2. It appears correct. And we use QuickFix to double-check our scopes or header/ids. Using scopes, it will read correctly in NVDA, except for the cell under the last RowSpan on top. If I down-arrow into that cell, it's in "Column 9." If I CTRL+ALT+Arrow into it, I get "edge of table."
The RowSpan for "Surplus," in the middle, with another ColSpan to the right, poses no issues. It's always the RowSpan(s) after a ColSpan ending the table at the top right.
(By the way, scopes are the way to go here. Use header/id, and the row header assignements on the left become a total mess, with the U.S. in Asia and the EuroZone.)
Alas, a workaround for this, besides your idea, is to split the top-right TH instead of doing the RowSpan. You still column-scope Employment, of course, There's a redundant "header" cell (blank TD) in row 2, but the "Displacement" problem goes away.
OK, Priyanka, I've posted the original Word File and PDF to the cloud ( https://files.acrobat.com/a/preview/7f566430-1364-4b3a-9d98-3c5461f55fe5 ).
There's another file "1a" with only the first table tagged. I cleaned this up and tried to make it PDF/UA compliant and couldn't. Will address in another post.
Thanks for sharing the files. Bug has been logged for this issue. We will update you soon with our findings.