diff -N DataQuality.lcsim
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ DataQuality.lcsim	22 Feb 2013 01:32:22 -0000	1.1
@@ -0,0 +1,18 @@

+<!-- 
+  Quick summary of file contents, to be run after readout simulation or reconstruction.
+  @author Sho Uemura <[log in to unmask]>
+  @version $Id: DataQuality.lcsim,v 1.1 2013/02/22 01:32:22 meeg Exp $
+-->
+<lcsim xmlns:xs="http://www.w3.org/2001/XMLSchema-instance" 
+       xs:noNamespaceSchemaLocation="http://www.lcsim.org/schemas/lcsim/1.0/lcsim.xsd">       
+    <control>
+        <printInputFiles>true</printInputFiles>
+        <printDriversDetailed>true</printDriversDetailed>
+    </control>    
+    <execute>
+        <driver name="CollectionSizeDriver"/>
+    </execute>    
+    <drivers>
+        <driver name="CollectionSizeDriver" type="org.lcsim.hps.util.CollectionSizeDriver"/>
+    </drivers>
+</lcsim>

diff -N CollectionSizeDriver.java
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ CollectionSizeDriver.java	22 Feb 2013 01:32:22 -0000	1.1
@@ -0,0 +1,73 @@

+package org.lcsim.hps.util;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.lcsim.event.EventHeader;
+import org.lcsim.util.Driver;
+
+/**
+ * Prints a summary of collections seen in the file, and their average sizes.
+ * @author Sho Uemura <[log in to unmask]>
+ * @version $Id: CollectionSizeDriver.java,v 1.1 2013/02/22 01:32:22 meeg Exp $
+ */
+public class CollectionSizeDriver extends Driver {
+
+    int eventCount = 0;
+    private Map<String, CollectionStats> collections = new HashMap<String, CollectionStats>();
+
+    @Override
+    public void process(EventHeader event) {
+        List<List<Object>> listOfLists = event.get(Object.class);
+        for (List<Object> list : listOfLists) {
+            String name = event.getMetaData(list).getName();
+            Class type = event.getMetaData(list).getType();
+
+            CollectionStats stats = collections.get(name);
+            if (stats == null) {
+                stats = new CollectionStats(name, type);
+                collections.put(name, stats);
+            }
+
+            stats.addCount(list.size());
+        }
+
+        eventCount++;
+    }
+
+    @Override
+    public void endOfData() {
+        List<String> names = new ArrayList<String>(collections.keySet());
+        java.util.Collections.sort(names);
+        for (String name:names){
+            collections.get(name).printStats(eventCount);
+        }
+    }
+
+    private class CollectionStats {
+
+        String name;
+        Class type;
+        double eventsWithCollection = 0;
+        double totalCount = 0;
+
+        public CollectionStats(String name, Class type) {
+            this.name = name;
+            this.type = type;
+        }
+
+        public void addCount(int count) {
+            eventsWithCollection++;
+            totalCount += count;
+        }
+
+        public void printStats(int eventCount) {
+            double fractionWithCollection = eventsWithCollection / eventCount;
+            double averageCollectionSize = totalCount / eventsWithCollection;
+
+            System.out.format("%s (%s): %f of events had this collection, with an average of %f elements\n", name, type.getSimpleName(), fractionWithCollection, averageCollectionSize);
+
+        }
+    }
+}