over the last century

[meliss]

Hi. Does it always mean "in 20th centuary" (so far) or it could be "over last 100 years"? Thank you.
"The volume of glaciers in the Caucasus has been reduced by 50 percent over the last century" (climate report)

 

[Raymott]

It should mean "over the last hundred years". That is not to say that that is the author's intention though.