County economies, the building blocks of the U.S. economy, grew in 2013, but there are still areas where the recovery is slow, a new report from the National Association of Counties (NACO) shows.

"As fiscal tightening continues to limit the scope of state and federal investment, it is becoming imperative for states and the federal government to work with counties to maintain the fundamentals of U.S. economy — county economies," Emilia Istrate, director of research at NACO, and Nicholas Lyell, a research associate at NACO, write in the report.

Istrate and Lyell analyzed annual changes of four economic performance indicators in 3,069 counties for the report: economic output (GDP), employment, unemployment rates and home prices. They found:

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• Recovery is still tenuous in some parts of the country despite continued growth in 2103. Economic output, jobs and home prices registered moderate growth in county economies, while unemployment fell in 2013 in all regions. Nearly half of the U.S. county economies, mostly in the South, did not have a recession or recovered their economic output that was lost due to the recession by 2013. Employment did not drop or were above their pre-recession levels in approximately 800 county economies, generally in the South and Midwest in 2013. Between 2012 and 2013, the housing sector's recovery rates were the highest among all the indicators analyzed. Pre-recession unemployment levels were reported in 54 county economies, mostly in the Midwest.

• Large Counties were at the center of the recession and the recovery. Out of the 3,069 county economies, 122 large-county economies — counties with more than 500,000 residents — produced roughly 58 percent of the county economies' GDP growth and a similar share of the added jobs during the recovery. The recovery was greatest in large-county economies, although they were hardest hit by the recession producing greater economic output, jobs and unemployment.

• Employment in medium-sized county economies was stable during the recession, but was varied in 2013. Nearly half of the 820 medium-sized-county economies — counties with populations between 50,000 and 500,000 residents — experienced shorter job recessions and registered job growth in 2013 than did the other county economies. But employment did not change or declined in 23 percent of the mid-sized counties.

• The recovery in small-county economies had just about equal outcomes by 2013. The majority of small-county economies grew in 2013, but a significant share saw stagnant or declining economic output and jobs. Two-thirds of this category registered expanding economic output and jobs and almost all of them had rising home prices. However, GDP declined in 27 percent of small-county economies, more than in any other county economy group. In addition, GDP was stagnant in another 10 percent of them. The decline in employment was less pronounced, with only 13 percent of small-county economies losing jobs, but this share was still larger than the average. According to the indicators, 28 percent of all small-county economies were on the path to recovery or still remained in recession.

Mountrail County, N.D., managed to slip by the recession, due to the natural gas boom for its economic performance, according to Time magazine.

Mountrail County, with a population of 9,000, is located in the northwestern part of the state on top of the Bakken shale formation.

It is the only county economy "in the country that experienced no signs of the recession," the report stated.

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