diff --git a/ledger/predict.go b/ledger/predict.go
index 3db8ade..5810c12 100644
--- a/ledger/predict.go
+++ b/ledger/predict.go
@@ -148,7 +148,7 @@ func BPIsWithFixedGrowthPrediction(bpis BPIs, window time.Duration, pattern stri
 			for _, predictionTime := range predictionTimes(window) {
 				k2 := predictionTime.Format("2006-01")
 				was := last[currency]
-				was.v *= 1.0 + apy
+				was.v *= 1.0 + (apy / 12.0)
 				result[currency][k2] = was.v
 				last[currency] = was
 			}