Los Angeles—Total paid search advertising spending across Google and Yahoo-Bing increased 21.6% in the first quarter compared with the year-earlier period, according to a report from search marketing agency the Search Agency. Mobile and tablets helped drive the growth, with total paid search advertising spending on smartphones up 68% in the first quarter compared with the year-earlier period. Total spending on tablets rose 135%. Tablet performance has increased steadily over the past five quarters, said Keith Wilson, VP-agency products at the Search Agency, in a statement. “I don't see this slowing anytime soon,” he said. The report is based on the Search Agency client data from U.S. campaigns.