**4. The Case of Norway: Competing Econometric Studies**

One interesting case concerns Norway, where gender quotas were imposed on listed companies a relatively long time ago—a 40% quota was imposed in 2003, becoming compulsory from 2008. A number of studies of Norway's gender balancing of corporate boards conclude that the gender quota law imposed large costs on the shareholders of firms. Eckbo et al. (2019) especially identify one paper by Ahern and Dittmar (2012) (AD), who state that their research reveals a causal effect of the imposition of the quota on (1) stock prices and on (2) companies' financial performance. Effect (1) occurred immediately after the announcement of the new law, while effect (2) was reflected in a significant decline in Tobin's *Q* in the following years. AD also maintain that the quota led to "younger and less experienced boards, increases in leverage and acquisitions, and deterioration in operating performance".

The AD study is strongly rooted in good econometric methodology, applied to a panel of 248 publicly listed companies in Norway for the period 2001–2009. The tools used include the event study on the stock price reaction to the initial announcement of the quota, the instrumental variable approach to investigate the "impact of the quota on Tobin's *Q*", the "effect of the quota on board characteristics", and the "effect of quota on firm policies", as well as the binomial logit for explaining companies' decisions to delist any time during the period 2003–2009. The AD paper appeared in the *Quarterly Journal of Economics* and has been widely cited and followed by other research in the area.

In the study by Eckbo et al. (2019), the authors use the AD data and perform a comprehensive new econometric analysis. In effect, the authors state that AD's results are not sustained when "simple econometric adjustments" are applied. Eckbo et al. (2019) use the same methodology as AD with refinements that (the authors claim) are necessary. For example, the event study has been repeated but with the use of a portfolio approach—which yielded insignificant abnormal returns to major quota-related news events—and also with adjustment for cross-correlation, resulting in insignificant abnormal returns as well. In addition, the instrumental variable approach to panel Tobin's *Q* regression resulted in an insignificant effect of the quota on *Q*. Finally, by using the diff-in-diff regression, the authors prove that, unlike AD, there is no significant change in CEO experience following the quota.

The discussion reported here is an example of results that differ even when using the same sample. Such a message is not very encouraging. Perhaps, wider use of good practices and extending the reasoning foundation into areas outside economics and finance may be an appropriate solution when conducting such research in the future.
