The number of births has declined 8 years in a row and we continue to see a record-low year after year.
There has been a new record-low number of birth every year for the last eight years.
この場合、次のような言い方ができますよ。
ーThe number of births has declined 8 years in a row and we continue to see a record-low year after year.
「出生数は8年連続で減少しており、過去最少を更新している」
the number of births「出生数」
8 years in a row「8年連続」
record-low「過去最少」
ーThere has been a new record-low number of birth every year for the last eight years.
「この8年間毎年、出生数の過去最少が記録されている」
for the last eight years「この8年間」
ご参考まで！
カナダ 
