Index: node_modules/d3-hierarchy/src/hierarchy/count.js
===================================================================
--- node_modules/d3-hierarchy/src/hierarchy/count.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
+++ node_modules/d3-hierarchy/src/hierarchy/count.js	(revision e4c61dd6cd86e06265bc2bd91adba84a0f04044a)
@@ -0,0 +1,12 @@
+function count(node) {
+  var sum = 0,
+      children = node.children,
+      i = children && children.length;
+  if (!i) sum = 1;
+  else while (--i >= 0) sum += children[i].value;
+  node.value = sum;
+}
+
+export default function() {
+  return this.eachAfter(count);
+}