B2B ad spending will increase 13 percent in 2018 to hit $4.6 billion from this year's estimated $4.07 billion, eMarketer has predicted. However, its proportion of all U.S. digital ad spending will remain unchanged at 4.9 percent, which implies growth in other digital ad spend areas as well. Desktops and laptops will continue to attract the bulk of B2B digital ad spend, according to eMarketer. They are expected to account for $2.54 billion this year. Mobile B2B digital ad spend, which is forecast to hit $1.53 billion this year, also will continue to grow.