Construction employment continued its spotty improvement in July, as more states posted year-over-year gains but most states posted decreases compared with June, according to an analysis by the Associated General Contractors of America of Labor Department data.

Association officials said the steady improvement in employment in many states was welcome news, but cautioned that the industry’s recovery was still fragile.

“Today’s report shows the fragile and fragmentary nature of the industry’s recovery,” said Ken Simonson, the association’s chief economist. “Construction employment increased in 37 states during the past 12 months — the largest number with gains since early last year—but only two states have surpassed their pre-recession peaks, and barely a third of states added construction jobs between June and July.”

Both the widespread annual gains and monthly losses were consistent with national totals for July, Simonson noted. Labor Department data released earlier this month showed construction employment rose 3.0% from July 2012 to July 2013, but slipped by 0.1%, seasonally adjusted, in the latest month.

The largest year-over-year percentage increase in construction jobs occurred in Wyoming (16.7%, 3,500 jobs), followed by Mississippi (12.3%, 5,800 jobs) and Hawaii (11.6%, 3,400 jobs). Texas added the most jobs over the past 12 months (33,100, 5.7%), followed by California (17,800, 3.0%) and Florida (15,700, 4.6%).

The District of Columbia and 13 states lost construction jobs from July 2012 to July 2013. The steepest declines occurred in Indiana (-6.7%, -8,300 jobs) and South Dakota (-6.7%, -1,400 jobs). The biggest losses were in Indiana and Ohio (-6,300, -3.5%).

Only 18 states added construction employees between June and July on a seasonally adjusted basis, while 30 states and D.C. lost jobs. There was no change in Massachusetts or Texas.

Three states had one-month employment gains of more than 3 percent: Kentucky (3.9%, 2,500 jobs), Hawaii (3.5%, 1,100 jobs) and Wyoming (3.4%, 800 jobs). Florida added the largest number of jobs for the month (3,700, 1.1%), followed by Georgia (2,600, 1.8%), Pennsylvania (2,600, 1.8%), Kentucky and Colorado (2,400, 1.9%).

The steepest one-month percentage decline in construction employment occurred in Montana (-4.1%, -900 jobs), followed by Idaho (-3.1%, -1,000 jobs). The largest drop in employment for the month occurred in California (-7,300, -1.2%), followed by Indiana (-3,400, -2.8%) and Ohio (-3,100, -1.8%).

Association officials said that after years of layoffs and slow demand, many unemployed skilled construction workers had likely either retired or switched industries. They noted that should demand for new construction expand, many firms indicate they are likely to face shortages of available skilled workers.

“While the industry’s recovery has been tentative and remains very fragile, any jump in demand would be as challenging for firms as it would be welcome,” said Stephen E. Sandherr, the association’s chief executive officer. “The biggest question for many firms is whether there will be enough skilled workers available if things heat up.”