According to Forrester's "The US Digital Marketing Forecast, 2018 to 2023," about half of marketers expect their search budgets to stay the same in 2019.

However, search ad budgets are predicted to shift to voice and voice-activated queries of voice assistants like Amazon's Alexa and Google Assistant will be mainstream in five years. Marketers will move from pay-per-click to voice skills, SEO, content on sites like Pinterest and branding to better capitalize on voice.

Amazon's growth is additionally boosted by consumer behavior. More shoppers now begin their purchasing journeys on Amazon than Google.

Related: Listen up: Voice search 101 for marketers