Scott Alexander analyzes birth order effects in SSC readers, finding strong effects for sibling age gaps of 1-7 years, with a significant drop-off after 7 years. Longer summary

Scott Alexander investigates birth order effects using data from the 2019 Slate Star Codex survey. He finds that firstborns are overrepresented among SSC readers, replicating previous findings. The study focuses on how age gaps between siblings affect this birth order effect. Results show strong effects for age gaps of 1-7 years, with a dramatic decrease for gaps larger than 7 years. Scott discusses possible explanations for these findings, including intra-family competition and parental investment hypotheses. He notes that the results don't seem consistent with some other proposed mechanisms like maternal antibodies or vitamin deficiencies. The post ends with a call for further replication and expansion of these results. Shorter summary