diff --git a/performance/compare.py b/performance/compare.py
index 5d0ad0c..1ed1984 100644
--- a/performance/compare.py
+++ b/performance/compare.py
@@ -1,3 +1,12 @@
+# This script requires pv.
+
+# https://www.ivarch.com/programs/pv.shtml
+
+# There is a Homebrew formula to install pv on macOS.
+
+# This script also depends on the simulation data:
+# make -C data
+
 import subprocess
 import sys
 
diff --git a/performance/data/.gitignore b/performance/data/.gitignore
index c54835f..3ab62c7 100644
--- a/performance/data/.gitignore
+++ b/performance/data/.gitignore
@@ -1,2 +1,3 @@
 *
 !Makefile
+!requirements.txt
diff --git a/performance/data/Makefile b/performance/data/Makefile
index 9765638..cabfc63 100644
--- a/performance/data/Makefile
+++ b/performance/data/Makefile
@@ -1,3 +1,14 @@
+# The make recipes require bcftools and bgzip.
+
+# https://samtools.github.io/bcftools/howtos/install.html
+# https://www.htslib.org/doc/bgzip.html
+
+# On macOS, there are Homebrew formulas for bcftools and htslib,
+# which contains bgzip.
+
+# The Python requirements are listed in requirements.txt:
+# pip install -r requirements.txt
+
 .PHONY: all clean
 
 all: sim_10k.vcz
diff --git a/performance/data/requirements.txt b/performance/data/requirements.txt
new file mode 100644
index 0000000..e6b46df
--- /dev/null
+++ b/performance/data/requirements.txt
@@ -0,0 +1,3 @@
+stdpopsim
+tskit
+bio2zarr