diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..c16bbae
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,11 @@
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[Makefile]
+indent_style = tab
diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index ef71177..9aeb3cc 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -16,8 +16,8 @@ jobs:
           #- windows-latest  # depext issue for gnuplot/jemalloc?
           #- macos-latest # slow
         ocaml-compiler:
-          - 4.08.x
           - 4.12.x
+          - 5.0.x
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v2
diff --git a/.gitignore b/.gitignore
index 61ae156..354d9c4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 .*.swp
 .*.swo
+_opam
 _build
 *.native
 *.byte
diff --git a/benchpress-server.opam b/benchpress-server.opam
index 121a4c5..03c237d 100644
--- a/benchpress-server.opam
+++ b/benchpress-server.opam
@@ -23,7 +23,7 @@ depends: [
   "tiny_httpd" { >= "0.12" & < "1.0" }
   "printbox" { >= "0.6" }
   "printbox-text" { >= "0.6" }
-  "ocaml" {>= "4.08" }
+  "ocaml" {>= "4.12" }
   "jemalloc" { >= "0.2" & < "0.3" }
 ]
 homepage: "https://github.com/sneeuwballen/benchpress/"
diff --git a/benchpress-worker.opam b/benchpress-worker.opam
index 37c4f1b..34ff98d 100644
--- a/benchpress-worker.opam
+++ b/benchpress-worker.opam
@@ -8,7 +8,7 @@ build: [
   ["dune" "build" "@doc" "-p" name] {with-doc}
 ]
 depends: [
-  "ocaml" {>= "4.08" }
+  "ocaml" {>= "4.12" }
   "dune" { >= "1.11" }
   "containers" { >= "3.0" & < "4.0" }
   "benchpress" { = version }
diff --git a/benchpress.opam b/benchpress.opam
index bf911c9..5df3525 100644
--- a/benchpress.opam
+++ b/benchpress.opam
@@ -28,7 +28,7 @@ depends: [
   "sqlite3_utils" { >= "0.4" & < "0.6" }
   "printbox" { >= "0.6" }
   "printbox-text" { >= "0.6" }
-  "ocaml" {>= "4.08" }
+  "ocaml" {>= "4.12" }
 ]
 homepage: "https://github.com/sneeuwballen/benchpress/"
 dev-repo: "git+https://github.com/sneeuwballen/benchpress.git"
diff --git a/src/bin/Show.ml b/src/bin/Show.ml
index 7d2b1bd..a235e17 100644
--- a/src/bin/Show.ml
+++ b/src/bin/Show.ml
@@ -1,13 +1,14 @@
 (* run tests, or compare results *)
 
 (* TODO: only load full results if needed *)
-let main ?(check = true) ?(bad = true) ?csv ?summary (file : string) : unit =
+let main ?(check = true) ?(bad = true) ~details ?csv ?summary (file : string) :
+    unit =
   Logs.debug (fun k -> k "loading file %S..." file);
   let res = Bin_utils.load_file file in
   Logs.debug (fun k -> k "loaded file %S" file);
   Bin_utils.dump_csv ~csv res;
   Bin_utils.dump_summary ~summary res;
-  Bin_utils.printbox_results res;
+  Bin_utils.printbox_results ~details res;
   if bad && not (Test_top_result.is_ok res) then
     Format.printf "@[<2>bad: %a@]@." Test_top_result.pp_bad res;
   if check then Bin_utils.check_res Notify.nil res;
diff --git a/src/bin/benchpress_bin.ml b/src/bin/benchpress_bin.ml
index 5c36aef..1f55696 100644
--- a/src/bin/benchpress_bin.ml
+++ b/src/bin/benchpress_bin.ml
@@ -382,16 +382,21 @@ module Show = struct
         value
         & opt (some string) None
         & info [ "summary" ] ~doc:"write summary in FILE")
-    and debug = Logs_cli.level () in
-    let aux check bad csv summary no_color debug file : bool =
+    and debug = Logs_cli.level ()
+    and details =
+      Arg.(value & flag & info [ "details" ] ~doc:"show more details")
+    in
+    let aux check bad csv summary no_color debug details file : bool =
       catch_err @@ fun () ->
       Misc.setup_logs debug;
       if no_color then CCFormat.set_color_default false;
-      Show.main ~check ~bad ?csv ?summary file
+      Show.main ~check ~bad ~details ?csv ?summary file
     in
     let doc = "show benchmark results (see `list-files`)" in
     Cmd.v (Cmd.info ~doc "show")
-      Term.(const aux $ check $ bad $ csv $ summary $ no_color $ debug $ file)
+      Term.(
+        const aux $ check $ bad $ csv $ summary $ no_color $ debug $ details
+        $ file)
 end
 
 (** {2 plot results} *)
diff --git a/src/core/Bin_utils.ml b/src/core/Bin_utils.ml
index d9c09c6..70205e9 100644
--- a/src/core/Bin_utils.ml
+++ b/src/core/Bin_utils.ml
@@ -92,8 +92,8 @@ let check_res ?(no_failure = false) notify (results : Test_top_result.t) : unit
   let a = Test_top_result.analyze results in
   check_res_an ~no_failure notify a
 
-let printbox_stat st : unit =
-  let box_st = Test_stat.to_printbox_l st in
+let printbox_stat ~details st : unit =
+  let box_st = Test_stat.to_printbox_l ~details st in
   Printf.printf "STAT:\n%s\n%!" (PrintBox_text.to_string box_st);
   ()
 
@@ -103,13 +103,13 @@ let printbox_analyze a =
   ()
 
 let printbox_compact_results (results : Test_compact_result.t) : unit =
-  printbox_stat results.cr_stat;
+  printbox_stat ~details:false results.cr_stat;
   printbox_analyze results.cr_analyze;
   ()
 
-let printbox_results (results : Test_top_result.t) : unit =
+let printbox_results ~details (results : Test_top_result.t) : unit =
   (let st = Test_top_result.stat results in
-   printbox_stat st);
+   printbox_stat ~details st);
   (let a = Test_top_result.analyze results in
    printbox_analyze a);
   ()
diff --git a/src/core/Test_stat.ml b/src/core/Test_stat.ml
index cca1599..913577b 100644
--- a/src/core/Test_stat.ml
+++ b/src/core/Test_stat.ml
@@ -2,16 +2,65 @@ open Common
 open Test
 module PB = PrintBox
 
+(** Aggregate function computing the mean and the standard deviation
+   of data series using the Welford's algorithm. *)
+module Stats = struct
+  type acc = { n: int; total: float; mean: float * float; s: float * float }
+
+  let prev = fst
+  let curr = snd
+  let init = { n = 0; total = 0.; mean = 0., 0.; s = 0., 0. }
+
+  let step ({ n; total; mean; s } as acc) x =
+    let x =
+      match x with
+      | Sqlite3.Data.FLOAT f -> f
+      | _ -> assert false
+    in
+    let n = n + 1 in
+    let total = total +. x in
+    if n = 1 then
+      { acc with n; total; mean = x, x }
+    else (
+      let new_mean = prev mean +. ((x -. prev mean) /. Float.of_int n) in
+      let new_s = prev s +. ((x -. prev mean) *. (x -. new_mean)) in
+      { n; total; mean = curr mean, new_mean; s = curr s, new_s }
+    )
+
+  let total { total; _ } = total
+
+  let mean { n; mean = _, mean; _ } =
+    if n = 0 then
+      0.
+    else
+      mean
+
+  let sd { n; s = _, s; _ } =
+    if n <= 1 then
+      0.
+    else
+      Float.(sqrt (s /. of_int (n - 1)))
+
+  let final acc =
+    let res = Fmt.asprintf "%f|%f|%f" (total acc) (mean acc) (sd acc) in
+    Sqlite3.Data.TEXT res
+
+  let attach_aggregate db =
+    Sqlite3.Aggregate.create_fun1 db ~init ~step ~final "stats"
+end
+
+type detail_stats = { n: int; total: float; mean: float; sd: float }
+
 type t = {
-  unsat: int;
-  sat: int;
+  unsat: detail_stats;
+  sat: detail_stats;
   errors: int;
-  unknown: int;
+  unknown: detail_stats;
   timeout: int;
   memory: int;
   valid_proof: int;
   invalid_proof: int;
-  custom: (string * int) list;
+  custom: (string * detail_stats) list;
   total: int;
   total_time: float; (* for sat+unsat *)
 }
@@ -24,11 +73,28 @@ let get_timeout r = r.timeout
 let get_valid_proof r = r.valid_proof
 let get_invalid_proof r = r.invalid_proof
 let get_memory r = r.memory
-let get_custom s r = try List.assoc s r.custom with Not_found -> 0
+
+let get_custom s r =
+  try List.assoc s r.custom
+  with Not_found -> { n = 0; total = 0.; mean = 0.; sd = 0. }
+
 let get_total r = r.total
 let get_total_time r = r.total_time
 
-let to_printbox_l ?to_link l : PB.t =
+let pb_details_stats_color ~details c { n; total; mean; sd } =
+  let open PB in
+  if n = 0 || not details then
+    align ~h:`Left ~v:`Center (int n)
+  else
+    v_record
+      [
+        "number", pb_int_color c n;
+        "total", text @@ Misc.human_duration total;
+        "mean", text @@ Misc.human_duration mean;
+        "deviation", text @@ Misc.human_duration sd;
+      ]
+
+let to_printbox_l ?(details = false) ?to_link l : PB.t =
   let mk_row ?res lbl get_r mk_box : PB.t list =
     match to_link with
     | Some f ->
@@ -47,13 +113,16 @@ let to_printbox_l ?to_link l : PB.t =
            l
     | _ -> PB.text lbl :: List.map (fun (_p, r) -> mk_box (get_r r)) l
   and mk_row1 lbl get_r mk_box =
-    PB.text lbl :: List.map (fun (_, r) -> mk_box @@ get_r r) l
+    PB.(align ~h:`Left ~v:`Center (text lbl))
+    :: List.map (fun (_, r) -> mk_box @@ get_r r) l
   in
   let r1 =
     [
-      mk_row "sat" get_sat @@ pb_int_color PB.Style.(fg_color Green);
-      mk_row "unsat" get_unsat @@ pb_int_color PB.Style.(fg_color Green);
-      mk_row1 "sat+unsat" (fun r -> r.sat + r.unsat)
+      mk_row1 "sat" get_sat
+      @@ pb_details_stats_color ~details PB.Style.(fg_color Green);
+      mk_row1 "unsat" get_unsat
+      @@ pb_details_stats_color ~details PB.Style.(fg_color Green);
+      mk_row1 "sat+unsat" (fun r -> r.sat.n + r.unsat.n)
       @@ pb_int_color PB.Style.(fg_color Green);
       mk_row ~res:"error" "errors" get_errors
       @@ pb_int_color PB.Style.(fg_color Cyan);
@@ -61,7 +130,8 @@ let to_printbox_l ?to_link l : PB.t =
       @@ pb_int_color PB.Style.(fg_color Green);
       mk_row1 "invalid_proof" get_invalid_proof
       @@ pb_int_color PB.Style.(fg_color Red);
-      mk_row "unknown" get_unknown PB.int;
+      mk_row1 "unknown" get_unknown
+      @@ pb_details_stats_color ~details PB.Style.(fg_color White);
       mk_row "timeout" get_timeout PB.int;
     ]
   and r2 =
@@ -70,7 +140,8 @@ let to_printbox_l ?to_link l : PB.t =
       |> CCList.sort_uniq ~cmp:String.compare
     in
     CCList.map
-      (fun tag -> mk_row ~res:tag ("tag." ^ tag) (get_custom tag) PB.int)
+      (fun tag ->
+        mk_row ~res:tag ("tag." ^ tag) (fun t -> (get_custom tag t).n) PB.int)
       all_custom
   and r3 =
     [
@@ -88,12 +159,23 @@ let to_printbox_l ?to_link l : PB.t =
 let of_db_for ~(prover : Prover.name) (db : Db.t) : t =
   Error.guard (Error.wrapf "reading stat(%s) from DB" prover) @@ fun () ->
   let custom = Prover.tags_of_db db in
+  Stats.attach_aggregate db;
+  let convert n stats =
+    let extract_stats stats =
+      String.split_on_char '|' stats |> List.map Float.of_string |> function
+      | [ total; mean; sd ] ->
+        { n = CCOpt.get_or ~default:0 n; total; mean; sd }
+      | _ -> assert false
+    in
+    extract_stats stats
+  in
   let get_res r =
     Error.guard (Error.wrapf "get-res %S" r) @@ fun () ->
     Logs.debug (fun k -> k "get-res %S" r);
-    Db.exec db {| select count(*) from prover_res where prover=? and res=?; |}
+    Db.exec db
+      {| select count(*), stats(rtime) from prover_res where prover=? and res=?; |}
       prover r
-      ~ty:Db.Ty.(p2 text text, p1 (nullable int), CCOpt.get_or ~default:0)
+      ~ty:Db.Ty.(p2 text text, p2 (nullable int) text, convert)
       ~f:Db.Cursor.get_one_exn
     |> Misc.unwrap_db (fun () -> spf "problems with result %s" r)
   in
@@ -119,15 +201,15 @@ let of_db_for ~(prover : Prover.name) (db : Db.t) : t =
   let sat = get_res "sat" in
   let unsat = get_res "unsat" in
   let unknown = get_res "unknown" in
-  let timeout = get_res "timeout" in
-  let memory = get_res "memory" in
-  let errors = get_res "error" in
+  let timeout = (get_res "timeout").n in
+  let memory = (get_res "memory").n in
+  let errors = (get_res "error").n in
   let valid_proof = get_proof_res "valid" in
   let invalid_proof = get_proof_res "invalid" in
   let custom = CCList.map (fun tag -> tag, get_res tag) custom in
   let total =
-    sat + unsat + unknown + timeout + memory + errors
-    + List.fold_left (fun n (_, i) -> n + i) 0 custom
+    sat.n + unsat.n + unknown.n + timeout + memory + errors
+    + List.fold_left (fun acc (_, { n; _ }) -> acc + n) 0 custom
   in
   let total_time =
     Db.exec db
@@ -164,7 +246,7 @@ let pp out (s : t) : unit =
     "(@[<hv>:unsat %d@ :sat %d@ :solved %d@ :errors %d@ :unknown %d@ \
      :valid-proof %d@ :invalid-proof %d@ :timeout %d@ :total %d@ :total_time \
      %.2f@])"
-    s.unsat s.sat (s.sat + s.unsat) s.errors s.unknown s.valid_proof
+    s.unsat.n s.sat.n (s.sat.n + s.unsat.n) s.errors s.unknown.n s.valid_proof
     s.invalid_proof s.timeout
-    (s.unsat + s.sat + s.errors + s.unknown + s.timeout)
+    (s.unsat.n + s.sat.n + s.errors + s.unknown.n + s.timeout)
     s.total_time
diff --git a/src/core/Test_stat.mli b/src/core/Test_stat.mli
index 821d179..907c52f 100644
--- a/src/core/Test_stat.mli
+++ b/src/core/Test_stat.mli
@@ -4,21 +4,25 @@ open Common
 open Test
 module PB = PrintBox
 
+type detail_stats = { n: int; total: float; mean: float; sd: float }
+
 type t = {
-  unsat: int;
-  sat: int;
+  unsat: detail_stats;
+  sat: detail_stats;
   errors: int;
-  unknown: int;
+  unknown: detail_stats;
   timeout: int;
   memory: int;
   valid_proof: int;
   invalid_proof: int;
-  custom: (string * int) list;
+  custom: (string * detail_stats) list;
   total: int;
   total_time: float; (* for sat+unsat *)
 }
 
-val to_printbox_l : ?to_link:prover_string_linker -> (string * t) list -> PB.t
+val to_printbox_l :
+  ?details:bool -> ?to_link:prover_string_linker -> (string * t) list -> PB.t
+
 val of_db_for : prover:Prover.name -> Db.t -> t
 val of_db : Db.t -> (Prover.name * t) list
 val pp : t Fmt.printer
diff --git a/tests/fake.expected b/tests/fake.expected
index dc05a70..f0f5751 100644
--- a/tests/fake.expected
+++ b/tests/fake.expected
@@ -3,9 +3,9 @@
 STAT:
 provers      │fake2│fake1
 ─────────────┼─────┼─────
-sat          │1    │1
+sat          │1    │1
 ─────────────┼─────┼─────
-unsat        │1    │1
+unsat        │1    │1
 ─────────────┼─────┼─────
 sat+unsat    │2    │2
 ─────────────┼─────┼─────