Apparently Rihanna and Taylor are serving their next efforts in Q4. (I'd include Adele, but she's an anomaly that would just make the comparison unbalanced)
I don't know if it's all that official (that both girls will released during the 4th quarter), but regardless, these 2 are the next big, successful names ready to SERVE.
So
Who, if at all, will most likely have the under-performing era?
I'm not necessarily referring to who will have the bigger/less sales either because they both have their own lane, so don't start comparing Rih's album sales to Taylor's as if we haven't tasted those teas. This is about who between the two will more likely fail to achieve the type of success they are used to having. It's possible they will both fail, and it is also possible they will both excel their previous efforts, but let's just pretend one of these 2 ARE going fail to achieve their typical standard, and be sure to choose wisely.
(Keep the decline in overall album sales in mind)
So, in Rih's case, an underperfoming era would be something like a #1-less era, failing to give us 250K first week, struggling to go platinum in the US.
In Taylor's case, an underperforming era would include no top 5 singles, with her albums first week failing to cross the 400K mark (I doubt she'll be able to repeat 1M FW during these rough times, so keep that in mind), struggling to go 2x platinum in the US.
Go
