diff --git a/Cargo.toml b/Cargo.toml
index 1793537..316b529 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -24,6 +24,7 @@ thiserror = "1.0.28"
 smol_str = { version = "0.1.17", default-features = false }
 indexmap = "1.7.0"
 bson = { version = "1.2.3", optional = true }
+nohash-hasher = "0.2.0"
 
 [dev-dependencies]
 color-eyre = "0.5.11"
@@ -33,5 +34,5 @@ indicatif = { version = "0.16.2", features = ["rayon"] }
 mongodb = { version = "2.0.2", default-features = false, features = ["sync"] }
 
 [profile.release]
-debug = true
+# debug = false
 # lto = true
diff --git a/examples/bag_info.rs b/examples/bag_info.rs
index 41f470d..bb534c3 100644
--- a/examples/bag_info.rs
+++ b/examples/bag_info.rs
@@ -15,6 +15,25 @@ fn main() -> Result<()> {
 
     let bag_path = &args[1];
     let mut bag = Bag::open(bag_path)?;
+    let chunk_positions = bag
+        .index()
+        .chunks
+        .iter()
+        .map(|chunk| chunk.pos)
+        .collect::<Vec<_>>();
+    let chunk_sizes = chunk_positions
+        .windows(2)
+        .map(|window| {
+            if let &[last, next] = window {
+                next - last
+            } else {
+                unreachable!();
+            }
+        })
+        .collect::<Vec<_>>();
+    let mean_chunk_size =
+        chunk_sizes.iter().map(|s| *s as f64).sum::<f64>() / (chunk_sizes.len() as f64);
+    info!("average chunk size: {}", mean_chunk_size);
 
     let info = bag.compute_info()?;
     info!("bag info: {:#?}", info);
diff --git a/examples/mongobag.rs b/examples/mongobag.rs
index acfc0a8..ee0f1d0 100644
--- a/examples/mongobag.rs
+++ b/examples/mongobag.rs
@@ -23,7 +23,7 @@ fn main() -> Result<()> {
     let layouts = bag.compute_message_layouts()?;
 
     let info = bag.compute_info()?;
-    let total_messages: u64 = info.per_connection.values().sum();
+    let total_messages: u64 = info.per_connection.values().map(|con| con.count).sum();
     info!("exporting {} messages", total_messages);
 
     let client = Client::with_uri_str("mongodb://localhost:27017")?;
diff --git a/src/info.rs b/src/info.rs
index a3e3d87..0b7ea8b 100644
--- a/src/info.rs
+++ b/src/info.rs
@@ -1,4 +1,5 @@
-use std::{collections::HashMap, io};
+use nohash_hasher::IntMap;
+use std::io;
 
 use rayon::prelude::*;
 
@@ -9,17 +10,26 @@ use crate::{
     Result,
 };
 
+#[derive(Default, Debug)]
+pub struct ConnectionStats {
+    pub count: u64,
+    pub unique_chunk_count: u64,
+}
+
 #[derive(Default, Debug)]
 pub struct BagInfo {
     pub total_uncompressed: u64,
-    pub per_connection: HashMap<u32, u64>,
+    pub per_connection: IntMap<u32, ConnectionStats>,
 }
 
 impl BagInfo {
+    // only info from disjoint chunks can be combined
     fn combine(mut self, other: BagInfo) -> BagInfo {
         self.total_uncompressed += other.total_uncompressed;
-        for (conn, count) in other.per_connection {
-            *self.per_connection.entry(conn).or_insert(0) += count;
+        for (conn, other_stats) in &other.per_connection {
+            let stats = self.per_connection.entry(*conn).or_default();
+            stats.count += other_stats.count;
+            stats.unique_chunk_count += other_stats.unique_chunk_count;
         }
         self
     }
@@ -39,8 +49,10 @@ impl BagInfo {
                 reader.skip_data()?;
                 for _ in &chunk.connections {
                     let index = IndexData::read(&mut reader)?;
-                    *info.per_connection.entry(index.conn_id).or_insert(0) +=
-                        index.entries.len() as u64;
+                    let stats = info.per_connection.entry(index.conn_id).or_default();
+                    stats.count += index.entries.len() as u64;
+                    // TODO: verify that each connection appears once
+                    stats.unique_chunk_count += 1;
                 }
                 Ok(info)
             })
@@ -55,8 +67,12 @@ impl BagInfo {
             .try_fold(BagInfo::default, |mut info, chunk| -> Result<_> {
                 let data = chunk?;
                 info.total_uncompressed += data.data.len() as u64;
-                let count = info.per_connection.entry(data.header.conn_id).or_insert(0);
-                *count += 1;
+                let stats = info
+                    .per_connection
+                    .entry(data.header.conn_id)
+                    .or_default();
+                stats.count += 1;
+                // TODO: stats.unique_chunk_count
                 Ok(info)
             })
             .try_reduce(BagInfo::default, |a, b| Ok(a.combine(b)))