diff --git a/common/workunit/workunit.cpp b/common/workunit/workunit.cpp
index 1f6c92c0fe2..beab6707501 100644
--- a/common/workunit/workunit.cpp
+++ b/common/workunit/workunit.cpp
@@ -2751,7 +2751,7 @@ class SubGraphUpdaterCollection : public CInterfaceOf<IStatisticCollection>
     {
         return rootCollection->addStatistic(kind,value);
     }
-    virtual void updateStatistic(StatisticKind kind, unsigned __int64 value, StatsMergeAction mergeAction) override
+    virtual bool updateStatistic(StatisticKind kind, unsigned __int64 value, StatsMergeAction mergeAction) override
     {
         return rootCollection->updateStatistic(kind, value, mergeAction);
     }
@@ -2879,8 +2879,8 @@ void updateAggregates(IWorkUnit *wu, GlobalStatisticCollection & statsCollection
     // 2) Serialize the aggregates into a blob in GraphProgress rather than to global stats
     std::vector<StatisticKind> aggregateKinds = {StCostFileAccess, StSizeGraphSpill, StSizeSpillFile};
     StatisticsAggregatesWriter statsAggregatorWriter(wu, aggregateKinds);
-    statsCollection.refreshAggregates(aggregateKinds);
-    statsCollection.visit(statsAggregatorWriter);
+    if(statsCollection.refreshAggregates(aggregateKinds)) // Only serialize if the aggregates has changed
+        statsCollection.visit(statsAggregatorWriter);
 }
 
 //---------------------------------------------------------------------------------------------------------------------
diff --git a/system/jlib/jstats.cpp b/system/jlib/jstats.cpp
index d105536fe87..f76e4e5ee87 100644
--- a/system/jlib/jstats.cpp
+++ b/system/jlib/jstats.cpp
@@ -1923,7 +1923,7 @@ class CStatisticCollection : public CInterfaceOf<IStatisticCollection>
         stats.append(s);
     }
 
-    void updateStatistic(StatisticKind kind, unsigned __int64 value, StatsMergeAction mergeAction)
+    virtual bool updateStatistic(StatisticKind kind, unsigned __int64 value, StatsMergeAction mergeAction) override
     {
         if (mergeAction != StatsMergeAppend)
         {
@@ -1932,13 +1932,19 @@ class CStatisticCollection : public CInterfaceOf<IStatisticCollection>
                 Statistic & cur = stats.element(i);
                 if (cur.kind == kind)
                 {
+                    if (mergeAction==StatsMergeReplace)
+                    {
+                        if (cur.value==value)
+                            return false;
+                    }
                     cur.value = mergeStatisticValue(cur.value, value, mergeAction);
-                    return;
+                    return true;
                 }
             }
         }
         Statistic s(kind, value);
         stats.append(s);
+        return true;
     }
 
     CStatisticCollection * ensureSubScope(const StatsScopeId & search, bool hasChildren)
@@ -2083,8 +2089,7 @@ class CStatisticCollection : public CInterfaceOf<IStatisticCollection>
                 if (iteratorVec!=aggregateKinds.end())
                 {
                     unsigned pos = iteratorVec-aggregateKinds.begin();
-                    StatsMergeAction mergeAction = queryMergeMode(kind);
-                    totals[pos] = mergeStatisticValue(totals[pos], stat.queryValue(), mergeAction);
+                    totals[pos] += stat.queryValue();
                     updated = true;
                 }
             }
@@ -2099,14 +2104,15 @@ class CStatisticCollection : public CInterfaceOf<IStatisticCollection>
             }
             if (updated)
             {
+                updated=false;
                 std::vector<unsigned __int64>::iterator totalIter = totals.begin();
                 std::vector<unsigned __int64>::iterator subTotalIter = childTotals.begin();
                 std::vector<StatisticKind>::iterator kindIter = aggregateKinds.begin();
                 while (totalIter != totals.end())
                 {
-                    StatsMergeAction mergeAction = queryMergeMode(*kindIter);
-                    updateStatistic(*kindIter, *subTotalIter, mergeAction);
-                    (*totalIter) = mergeStatisticValue(*totalIter, *subTotalIter, mergeAction);
+                    if (updateStatistic(*kindIter, *subTotalIter, StatsMergeReplace))
+                        updated=true;
+                    (*totalIter) += *subTotalIter;
 
                     ++totalIter;
                     ++subTotalIter;
diff --git a/system/jlib/jstats.h b/system/jlib/jstats.h
index 5d775fbd3bb..ffcadc15ca9 100644
--- a/system/jlib/jstats.h
+++ b/system/jlib/jstats.h
@@ -125,7 +125,7 @@ interface IStatisticCollection : public IInterface
     virtual void visitChildren(IStatisticVisitor & target) const = 0;
     virtual IStatisticCollection * ensureSubScope(const StatsScopeId & search, bool hasChildren) = 0;
     virtual void addStatistic(StatisticKind kind, unsigned __int64 value) = 0;
-    virtual void updateStatistic(StatisticKind kind, unsigned __int64 value, StatsMergeAction mergeAction) = 0;
+    virtual bool updateStatistic(StatisticKind kind, unsigned __int64 value, StatsMergeAction mergeAction) = 0;
     virtual bool refreshAggregates(std::vector<StatisticKind> & aggregateKinds, std::vector<unsigned __int64> & totals) = 0;
     virtual void deserialize(MemoryBuffer & in, unsigned version, StatisticScopeType minScope=SSTnone) = 0;
     virtual void deserializeChild(StatsScopeId scopeId, MemoryBuffer & in, unsigned version, StatisticScopeType minScope=SSTnone) = 0;