and measured.

To investigate the potential of redshift dependent sample biases on our metallicity distributions we therefore compare the following populations for the described reasons:

-   We begin by plotting the redshift distributions of the LGRB host galaxy populations for which we have host metallicity measurements. Since [@xshooter_survey] has approximately three times as many objects, we use this as the numeric baseline and scale the sample of [@stats_paper] by a factor of 0.7 to match.

-   To address concerns about a metallicity dependent redshift bias we also plot the subset of [@xshooter_survey] hosts with metallicities above solar. As this is only about a third of the total [@xshooter_survey] host population, it is scaled by a factor of three. We also plot the subset of [@xshooter_survey] hosts with metallicities above $ {\rm log(O/H)}+12 > 8.4 $ (KK04 scale) so as to sample only objects clearly above the $ {\rm log(O/H)}+12 \approx 8.3 $ metallicity cutoff noted in [@diff_rate_letter]. Similar high metallicity subsets of the [@stats_paper] sample is omitted due to its small size of only two and four objects (after the removal of LGRB 020819B).

-   To address concerns about a bias in which objects have the lines needed for metallicity 