increase in表示“在……方面增长”,increase by是“增长了多少”（by表示差额）,increase with表示“随……增长”,如：
Activists are increasing in number day by day.
His vanity increased with years.
The per unit area yield of ginned cotton has increased by 10% over last year.
希望我能帮助你解疑释惑. increase in表示“在……方面增长”,increase by是“增长了多少”（by表示差额）,increase with表示“随……增长”,如：
Activists are increasing in number day by day.
His vanity increased with years.
The per unit area yield of ginned cotton has increased by 10% over last year.
希望我能帮助你解疑释惑.