measurement we plot the entire [@xshooter_survey] host population including the objects without a metallicity. Since metallicity measurement requires a specific set of lines whereas redshift measurement requires only a single identified line (in practice any two lines is used to identify both the lines and the redshift) this provides an immediate crosscheck on observational biases in line measurement. As including [@xshooter_survey] objects with redshift but not metallicity makes an approximate 50% increase in the sample size (at z $<$ 2.5 before the slope noticeably changes) we scale it down by a factor of $\frac{2}{3}$. As the slope of this, and some other distributions, noticeably changes at z $\approx$ 2.5, and since z $\approx$ 2.5 is the limit of the redshift range for which we have measured metallicities, we adopt this redshift, along with the matching ordinate of this distribution (a value of $\sim$60), as the reference point for scaling the remaining distributions.

-   Next we compare it with the general burst population by plotting all known LGRB host galaxy redshifts as conveniently complied in the GRB table of Jochen Greiner[^3] (excluding for this and all other samples those objects with no or only photometric redshifts), as of UTC noon March 