Nouns ending in -ie are usually feminine.
The suffix often names an abstract quality, an activity, or a discipline.
Is économie masculine or feminine?
l'économie
The rule behind it
95.7% of -ie nouns are feminine
In context
Il garde toutes ses économies à la banque.
He keeps all his savings in the bank.
La grève a nui à l'économie nationale.
The strike affected the nation's economy.
L'économie du pays dépend de l'agriculture.
The country's economy depends on agriculture.