Click-through rates continue to decline, but marketers keep increasing budgets for paid-search ads running on Google and Bing. Could that mean the cost to seal the deal with a customer keeps rising. It’s unclear by how much as both companies push mobile advertising.

Marin Software released its Q1 2019 Digital Benchmark Report Tuesday, which analyzes its customers’ search, mobile and social performance data. The aggregated data shows that click volume on Bing and Google rose to 108.4 during the first quarter of 2019, up from 100 in the year-ago quarter. The click data during the holiday quarter in 2018 came in at 106.7.

Marin shows that the click volume for the second quarter of 2018 tanked at 95, so it will be interesting to see the second-quarter data for 2019.

Separately, Google click volume rose to 109.2 in the quarter, up from 108.3 in the prior quarter. Bing rose slightly to 99.8, up from 99.7. In the third quarter of 2018, Bing peaked at 102.2 in click volume.

The cost per click (CPC) fell 6% to $0.67 in the first quarter of 2019, compared with the fourth quarter of 2018. In fact, CPCs, overall, have been falling since the second quarter in 2018.

Brian Finnerty, senior director of marketing at Marin, attributes the decline in CPCs to an increase in mobile search advertising. CPCs on mobile are lower.

Travel CPCs came in at $0.31 and retail CPCs at $0.39. Both were lower in the first quarter of 2019, compared with the prior quarter, as inventory because less expensive outside of the peak holiday season, according to the report.

While Finnerty admits that the company is not seeing any slowdown in digital ad spend, overall click-through rates also declined. In fact, CTRs fell to 3.05, compared with 3.53 in the year-ago quarter.

The bigger surprise was the number of marketers using responsive search ads — about one-quarter of Marin’s clients.

Mobile search continues to rise, accounting for 43% of the amount spent in the quarter, up from 41% in the prior quarter, across all types of companies that Marin supports.

About 22% of advertisers ran Google Shopping Ads, with the format taking 39% of search budgets, up from 36% in the prior quarter and 33% in the year-ago quarter.