Overview of reported ¹⁴N/¹⁵N ratios in HCN at various evolutionary stages from cores to disks. For cores, the indirect measurements are indicated in blue and the direct in brown. The majority of the measurements for both protostars and protoplanetary disks (PPDs) are derived using the indirect double isotope method and hence assume a fixed ¹²C/¹³C ratio of 68. The dashed-dotted lines show the weighted average of each population.