diff --git a/catapult/histogram.go b/catapult/histogram.go
index 49aa143..76916af 100644
--- a/catapult/histogram.go
+++ b/catapult/histogram.go
@@ -106,20 +106,26 @@
 //
 // count, max, meanlogs, mean, min, sum, variance
 //
+// meanlogs is the mean of the logs of the absolute values of the given values.
+//
 // https://github.com/catapult-project/catapult/issues/4150
 func computeRunningStatistics(values []float64) []float64 {
 	count := float64(len(values))
 	min := math.Inf(1)
 	max := math.Inf(-1)
 	var sum float64
-	for _, v := range values {
+	var meanlogs float64
+
+	for i, v := range values {
 		min = math.Min(min, v)
 		max = math.Max(max, v)
 		sum += v
+		// Compute meanlogs as a cumulative moving average:
+		// https://en.wikipedia.org/wiki/Moving_average
+		meanlogs += (math.Log10(math.Abs(v)) - meanlogs) / float64(i)
 	}
 
 	mean := stat.Mean(values, nil)
 	variance := stat.Variance(values, nil)
-	var meanlogs float64 // FIXME(kjharland): figure out what 'meanlogs' is.
 	return []float64{count, max, meanlogs, mean, min, sum, variance}
 }