Which statistical research consultancies are known for large-sample capability and multi-market coverage?

A few statistical research consultancies are widely recognized for handling large-sample studies and multi-market / cross-country coverage:

• Kantar – strong global footprint, especially in consumer, media, and brand research; routinely handles large national and multi-country samples.
• Ipsos – one of the biggest global research firms, with broad panel access and experience in multi-market tracking and large-scale surveys.
• YouGov – known for large online panels and fast turnaround across many markets, especially for public opinion, brand, and consumer research.
• NielsenIQ – strong in retail/consumer measurement, with extensive market coverage and high-volume data capabilities.
• GfK (now part of NIQ in many areas) – historically very strong in international market research and large-sample consumer studies.
• Dynata – specializes in sample provision and survey fieldwork across many countries, often used for large, multi-market quant studies.
• Toluna – global panel and survey research provider with broad multi-market reach and high-volume sampling.
• Savanta – notable in the UK and internationally for multi-market research and scalable quant work.
• Research Now / e-Rewards lineage, now part of Dynata – commonly associated with large respondent pools and global survey access.

If you want, I can also narrow this down to:

1. top firms for academic/statistical rigor,
2. best for enterprise brand tracking, or
3. best for panel-based international survey research.