San Luis Obispo is California’s fastest-growing county, with Lake in second place and Placer in third, the Center for the Continuing Study of the California Economy reported. The Palo Alto-based center said it calculated the rankings by combining the percentage increases in population, taxable retail sales, per capita income and salaried jobs since 1980. “San Luis Obispo topped the growth index by ranking second in job and retail sales growth, fifth in per capita income increases and seventh in population gains,” said Stephen Levy, principal author of the report. The other high-ranking counties were, in order: Santa Clara, Sonoma, Riverside, Santa Cruz, Ventura, San Diego and Solano. Lake ranked first in population growth with an increase of 29.3%. Placer was No. 1 in retail sales with a 56.5% increase.