Riddell and Rid- dell’s study of union density in both the USA and Canada be- tween 1984 and 1998 found that none of the decline in Can- ada’s unionization rate was the result of declines in industries with a propensity for unionization. [...] The results showed that not only was the change in cer- tification procedure almost entirely responsible for changes in certification success rate, but the introduction of mandatory vote doubled the effectiveness of management opposition (as measured through the frequency of ULP complaints). [...] As noted above, the lack of data on the number of employees in proposed bargaining units is an impediment to determining if declines in certifications are the result of de- creased demand for unionization, declines in small firms or impediments to organizing small bargaining units. [...] It is quite likely that this increase in decertification applica- tions was the result of the lowering of the threshold number of employees needed to decertify a bargaining agent. [...] The trend in the decertification success rate largely follows the trend in decertification applications; how- ever, there was a second decline in the success rate following 2007.