Historical metrics options.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v26/common/keyword_plan_common.proto)

| Fields ||
|---|---|
| ## `include_average_cpc` | `bool` Indicates whether to include average cost per click value. Average CPC is provided only for legacy support. |
| ## `year_month_range` | `https://developers.google.com/google-ads/api/reference/rpc/v26/YearMonthRange` The year month range for historical metrics. If not specified, metrics for the past 12 months are returned. Search metrics are available for the past 4 years. If the search volume is not available for the entire year_month_range provided, the subset of the year month range for which search volume is available are returned. |