This story is available exclusively to Insider subscribers. Become an Insider and start reading now. Billions in advertising will be up for grabs this year as a rash of brands look for new agencies. The trend follows a slow 2020, when many marketers cut budgets and paused agency searches. Coca-Cola, JetBlue, and Walmart are among the most valuable accounts up for grabs. Advertisers slashed their budgets during the pandemic while suspending the long and expensive process of changing ad agencies. But 2021 is expected to be an unusually active year for new business with billions in ad spending expected to change agency hands.