Additions to private-sector membership rate from inflow of NLRB elections, 1951–2017
| Time period | Organizing additions to density, 10–year rate |
|---|---|
| 1951–1960 | 8.7% |
| 1960–1970 | 5.5% |
| 1970–1980 | 3.2% |
| 1980–1990 | 1.2% |
| 1990–2000 | 0.9% |
| 2000–2007 | 0.8% |
| 2007–2017 | 0.5% |
Source: National Labor Relations Board data. See appendix. Organizing inflow from number of voters in NLRB units that chose collective bargaining and does not take first contracts into account.