Final answer:
To decide on expanding advertising to new markets, one should analyze Location and Language reports for insights on visitor demographics and Source/Medium reports to evaluate current advertising effectiveness and potential new opportunities.
Step-by-step explanation:
When considering the expansion of advertising to new markets, Location and Language reports would be essential. These reports provide insights into where current site visitors are located and what languages they speak, helping to identify potential new markets with high user engagement. Additionally, Source/Medium reports are valuable as they display how visitors find your site, showing the effectiveness of current advertising efforts and highlighting opportunities for expansion. Frequency and recency reports could also be used as supplementary data to understand the behavior of repeat visitors, although they are not as directly related to the decision of expanding to new markets as Location and Language or Source/Medium reports.