expression
year after year; with each passing year
Describes a gradual change or progression that occurs as years go by. Often used with verbs indicating increase, decrease, or change.
年を追うごとに、彼の技術は向上している。
His skills are improving year after year.
年を追うごとに、この町の人口は減っている。
The population of this town is decreasing with each passing year.
A set phrase composed of 年 (year), を (object marker), 追う (to chase, to follow), and ごとに (each time). Literally 'each time one chases the years', it conveys the idea of something happening as years pass.