This is based on the Consumer Price Index, the average change in prices that people in a city might see on the goods and services they regularly buy.

这是基于消费者价格指数，即从一个城市的居民在经常购买的商品和服务上可以得出的平均价格变化。

Circulating the dielectric oil helps to keep  the temperature within the pipe consistent along the line, but can't control how that average  temperature changes over time.

循环介电油有助于保持管道内的温度沿线一致，但无法控制平均温度随时间的变化。