It's quite usual to wait this long after a huge album like 21.

Michael Jackson waited 5 years after Thriller to release Bad. Shania Twain did the same between Come On Over and Up!. Shakira waited 4 years after Laundry Service. It's a smart move.

I don't get how that proves it's a smart move?

How did the follow up albums do? Anyways its a smart move because of over exposure.

Didn't the Thriller era and Shania's era last like 2-3 years tho? So the wait till the next album really wasn't that long when you go from the last single falling off the charts.

Bad sold about 35 million, a little over half of Thriller. Up! did about 15 million, probably a little less than half of Come On Over.

The technical wait time wait time between 21 and her third album would match that of Thriller to Bad were it to be released in October 2015 (4 years and 9 months) and that of Come on Over to Up! in like January 2016 (5 years).