Three of the markets – Los Angeles, Baltimore and San Antonio – have been accredited for the first time, while Riverside-San Bernardino and Tampa-St Petersburg-Clearwater have regained accreditation after losing it in January.

Following the latest MRC accreditations, there are now 14 Arbitron markets that have been accredited leaving 34 without.

Arbitron’s chief researcher Gregg Lindner said: “”We are pleased the MRC has recognised the progress we have made; at the same time we understand there is still work to be done. We will continue our efforts to maintain the MRC double checkmarks in our currently accredited PPM markets and to achieve service-wide accreditation for all PPM markets.”

Meanwhile, Arbitron has posted a 31% increase in net income and a 9% rise in revenue for the second quarter of 2012. Net income was up to $10m compared to $7.6m in the same period last year while revenue stood at $104.4m from $95.7m in 2011.

The firm said that annual price escalators in multi-year radio ratings contracts, the phasing-in of price increases for the PPM service and a growth in cross-platform and mobile business contributed to the revenue increase.

For the first six months of the year, net income increased 16.5% from $23.8m to $27.8m and revenue was up 7.2% from $196.6m to $210.8m.

President and CEO William Kerr said: “Throughout the second quarter, we remained focused on our longstanding priorities: pursuing opportunities for revenue growth while enhancing the value and utility of our core services.”