The business wants to see the last 12 months of credit card spend split across three channels: online, in-store, and cross-border. A colleague built 12 pie charts, one per month. For example, online was 40% in January and 52% in December. The boss says it's hard to see any trend. What chart would you use instead, and why?

业务方要看过去12个月的信用卡消费，分线上、线下门店、境外三个渠道。同事做了12个饼图，每月一个，比如1月线上占40%，12月占52%。老板说看不出趋势。你会换成什么图？为什么？