diff --git a/segeval/agreement/pi.py b/segeval/agreement/pi.py
index 791b31b..a72062a 100644
--- a/segeval/agreement/pi.py
+++ b/segeval/agreement/pi.py
@@ -6,6 +6,7 @@
 from __future__ import absolute_import, division
 from decimal import Decimal
 from segeval.agreement import __fnc_metric__, __actual_agreement_linear__
+from itertools import chain
 
 
 def __fleiss_pi_linear__(dataset, **kwargs):
@@ -29,13 +30,10 @@ def __fleiss_pi_linear__(dataset, **kwargs):
     A_a = Decimal(sum(all_numerators)) / sum(all_denominators)
     # Calculate Ae
     p_e_segs = list()
-    for boundaries_info in coders_boundaries.values():
-        for item in boundaries_info:
-            boundaries, total_boundaries = item
-            p_e_seg = Decimal(boundaries) / total_boundaries
-            p_e_segs.append(p_e_seg)
+    boundary_ratios = chain.from_iterable(coders_boundaries.values())
+    b_placed, b_possible = map(sum, zip(*boundary_ratios))
     # Calculate P_e_seg
-    P_e_seg = Decimal(sum(p_e_segs)) / len(p_e_segs)
+    P_e_seg = Decimal(b_placed) / b_possible
     A_e = (P_e_seg ** 2)
     # Calculate pi
     pi = (A_a - A_e) / (Decimal('1') - A_e)
diff --git a/segeval/similarity/__init__.py b/segeval/similarity/__init__.py
index 220811b..185accc 100644
--- a/segeval/similarity/__init__.py
+++ b/segeval/similarity/__init__.py
@@ -103,7 +103,7 @@ def __boundary_confusion_matrix__(*args, **kwargs):
     # Add weighted near misses
     for transposition in statistics['transpositions']:
         match = transposition[2]
-        matrix[match][match] += fnc_weight_t([transposition], n_t)
+        matrix[match][match] += (1 - fnc_weight_t([transposition], n_t))
     # Add confusion errors
     for substitution in statistics['substitutions']:
         hyp, ref = substitution
@@ -113,11 +113,11 @@ def __boundary_confusion_matrix__(*args, **kwargs):
         hyp, ref = None, None
         boundary_type, side = addition
         if side == 'a':
-            hyp = None
-            ref = boundary_type
-        else:  # side == 'b'
             hyp = boundary_type
             ref = None
+        else:  # side == 'b'
+            hyp = None
+            ref = boundary_type
         assert side == 'a' or side == 'b'
         matrix[hyp][ref] += 1
     return matrix