Looking on the internet deeply has found these results:

over the past decade is the most popular phrase on the web.

over the past decades 14,500,000 results on the web	over the past decade 123,700,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
reside in Europe. 64 million Indeed, labour migration has steadily increased over the past decades, and most of the world's migrants 64 million Hungary is indeed where ethnic minorities have been almost completely eliminated over the past decades. Remarkable successes have been achieved here over the past decades. whereas labour migration has steadily increased over the past decades and nowadays most of the world's international migrants reside in the European Union,	It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

over the past decades

14,500,000 results on the web

over the past decade

123,700,000 results on the web

More popular!

reside in Europe.
64 million
Indeed, labour migration has steadily increased over the past decades, and most of the world's migrants
64 million
Hungary is indeed where ethnic minorities have been almost completely eliminated over the past decades.
Remarkable successes have been achieved here over the past decades.
whereas labour migration has steadily increased over the past decades and nowadays most of the world's international migrants
reside in the European Union,

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.