Tax collections from oil and gas production last year were more than 10 percent off the previous year, though the Oklahoma state treasury expressed optimism. S&P Global Ratings lowered its credit rating for Oklahoma by one notch to AA- last week, but kept its outlook stable. The ratings agency said the state economy is diversifying away from oil and gas, but some metrics show a state of contraction against growth in the national economy. The state government reported taxes on oil and gas production in February were up 32.4 percent year-over-year and 14.7 percent higher than from January. For full-year 2016, tax collections brought in $367.3 million, down 12.4 percent from the previous 12-month period. […]