5.122 development and regular occurrence

To indicate that something develops gradually, or happens at regular intervals, you can use a general time word with 'by' followed by same general time word.

• She was getting older year by year, and lonelier, and more ridiculous.
• Millions of citizens follow, day by day, the unfolding of the drama.

Gradual development can also be indicated by the adverbs 'increasingly' and 'progressively'.

• ...the computers and information banks upon which our world will increasingly depend.
• His conduct became increasingly eccentric.
• As disposable income rises, people become progressively less concerned with price.