21st Century Insurance Group turned in a lackluster second quarter as earnings dipped slightly and premiums written remained virtually unchanged versus the year ago period. The Woodland Hills-based auto insurance carrier said it earned $20.5 million or $0.24 per share for the second quarter ended June 30, 2005, a 4 percent decline compared to $21.4 million or $0.25 per share for the same period a year ago. For the six months, 21st Century reported earnings of $39.9 million or $0.47 per share, compared to $41.2 million or $0.48 per share for the first six months of 2004. 21st Century, which specializes in personal auto insurance, wrote $328.7 million worth of premiums in the quarter, 1.2 percent more than the $324.8 million the company wrote in the second quarter of last year.