diff --git a/Hash2Pub.cabal b/Hash2Pub.cabal
index f7a1676..92ec096 100644
--- a/Hash2Pub.cabal
+++ b/Hash2Pub.cabal
@@ -46,7 +46,7 @@ category:            Network
 extra-source-files:  CHANGELOG.md
 
 common deps
-  build-depends:       base ^>=4.12.0.0, containers ^>=0.6.0.1, bytestring, utf8-string ^>=1.0.1.1, network ^>=2.8.0.1, time ^>=1.8.0.2, cmdargs ^>= 0.10, cryptonite ^>= 0.25, memory, async, stm, asn1-encoding, asn1-types, asn1-parse, publicsuffix, network-byte-order, safe, iproute, mtl, random, servant, servant-server, servant-client, warp, text, unordered-containers, hashable, unicode-transforms, http-client, http-types, unbounded-delays, dlist
+  build-depends:       base ^>=4.12.0.0, containers ^>=0.6.0.1, bytestring, utf8-string ^>=1.0.1.1, network ^>=2.8.0.1, time ^>=1.8.0.2, cmdargs ^>= 0.10, cryptonite ^>= 0.25, memory, async, stm, asn1-encoding, asn1-types, asn1-parse, publicsuffix, network-byte-order, safe, iproute, mtl, random, servant, servant-server, servant-client, warp, text, unordered-containers, hashable, unicode-transforms, http-client, http-types, unbounded-delays, dlist, formatting
   ghc-options:         -Wall -Wpartial-fields
 
 
diff --git a/src/Hash2Pub/PostService.hs b/src/Hash2Pub/PostService.hs
index 2170945..662b0a1 100644
--- a/src/Hash2Pub/PostService.hs
+++ b/src/Hash2Pub/PostService.hs
@@ -35,6 +35,7 @@ import qualified Network.HTTP.Types        as HTTPT
 import           System.Random
 import           Text.Read                 (readEither)
 
+import           Formatting                (float, format, (%), fixed)
 import qualified Network.Wai.Handler.Warp  as Warp
 import           Servant
 import           Servant.Client
@@ -113,7 +114,10 @@ instance DHT d => Service PostService d where
             port' = fromIntegral (confServicePort conf)
             warpSettings = Warp.setPort port' . Warp.setHost (fromString . confServiceHost $ conf) $ Warp.defaultSettings
         -- log a start message, this also truncates existing files
-        TxtI.writeFile (confLogfilePath conf) "# Starting mock relay implementation\n"
+        TxtI.writeFile (confLogfilePath conf) $ Txt.unlines
+            [ "# Starting mock relay implementation\n"
+            , "#relay receive rate   ;relay delivery rate   ;instance publish rate ;instance fetch rate"
+            ]
         -- Run 'concurrently_' from another thread to be able to return the
         -- 'PostService'.
         -- Terminating that parent thread will make all child threads terminate as well.
@@ -813,12 +817,11 @@ evaluateStatsThread serv statsAcc = getPOSIXTime >>= loop
           -- format: total relayReceiveRates;total relayDeliveryRates;postFetchRate;postPublishRate
           -- later: current (reported) load, target load
           TxtI.appendFile (confLogfilePath . serviceConf $ serv) $
-              Txt.intercalate ";" (Txt.pack <$> (
-              [ show . sum . relayReceiveRates
-              , show . sum . relayDeliveryRates
-              , show . postPublishRate
-              , show . postFetchRate
-              ] <*> pure rateStats)) <> "\n"
+              format ((fixed 20) % ";" % (fixed 20) % ";" % (fixed 20) % ";" % (fixed 20) % "\n")
+                  (sum . relayReceiveRates $ rateStats)
+                  (sum . relayDeliveryRates $ rateStats)
+                  (postPublishRate rateStats)
+                  (postFetchRate rateStats)
           loop now