Union-representation petitions filed by workers with the National Labor Relations Board have been essentially flat through the first three-quarters of the fiscal year, a big slowdown in growth from the 58% increase recorded in the same nine months a year earlier.

But employment lawyers tracking the activity say it would be wrong to interpret the lull as indicating that unionizing efforts are losing momentum. Petition filings through the first nine months ending June 30 totaled 1,904, higher than the full year for all but four of the past 10 years. Petitions totaled 1,892 in the same nine months a year earlier.