I made this post just for fun using Google Trends
I put other artists for comparison purposes (don't get angry).
This is global data (Not Japan only).
ayumi hamasaki
ayu's popularity search index had its peak during May 2019
ayumi hamasaki vs. Namie Amuro & Koda Kumi
ayumi hamasaki 46% average
namie amuro 35% average
koda kumi 16% average
ayumi hamasaki vs. AKB48
ayu 46%
Maeda Atsuko (AKB48's most popular member of all times) 11% average
Rino Sashihara (AKB48's 2nd most popular member) 9% average
ayumi hamasaki vs. best-selling female solo singers
ayu 46% average
nana 23% average
aoi 17% average