diff --git a/synthpop/ipf/ipf.py b/synthpop/ipf/ipf.py
index b3beddb..67715e5 100644
--- a/synthpop/ipf/ipf.py
+++ b/synthpop/ipf/ipf.py
@@ -52,6 +52,12 @@ def calc_diff(x, y):
 
     iterations = 0
 
+    sums = marginals.groupby(level=0).sum()
+    if sums.max() - sums.min() > 0.01:
+        raise RuntimeError(
+            'Marginals do not add up ipf will not converge: {}'.format(sums))
+    del sums
+
     list_of_loc = [
         ((flat_joint_dist[idx[0]] == idx[1]).values, marginals[idx])
         for idx in marginals.index
diff --git a/synthpop/ipf/test/test_ipf.py b/synthpop/ipf/test/test_ipf.py
index f30142b..ce15175 100644
--- a/synthpop/ipf/test/test_ipf.py
+++ b/synthpop/ipf/test/test_ipf.py
@@ -45,3 +45,22 @@ def test_larger_ipf():
 
     with pytest.raises(RuntimeError):
         ipf.calculate_constraints(marginals, joint_dist, max_iterations=2)
+
+
+def test_not_add_ipf():
+    # Test IPF with some data that's slightly more meaningful,
+    # but for which it's harder to know the actual correct answer.
+    marginal_midx = pd.MultiIndex.from_tuples(
+        [('cat_owner', 'yes'),
+         ('cat_owner', 'no'),
+         ('car_color', 'blue'),
+         ('car_color', 'red'),
+         ('car_color', 'green')])
+    marginals = pd.Series([60, 40, 50, 31, 20], index=marginal_midx)
+    joint_dist_midx = pd.MultiIndex.from_product(
+        [('yes', 'no'), ('blue', 'red', 'green')],
+        names=['cat_owner', 'car_color'])
+    joint_dist = pd.Series([8, 4, 2, 5, 3, 2], index=joint_dist_midx)
+
+    with pytest.raises(RuntimeError):
+        ipf.calculate_constraints(marginals, joint_dist)
diff --git a/synthpop/recipes/starter.py b/synthpop/recipes/starter.py
index 5c7bf39..a4b161b 100644
--- a/synthpop/recipes/starter.py
+++ b/synthpop/recipes/starter.py
@@ -69,10 +69,10 @@ def __init__(self, key, state, county, tract=None):
                                  "+ B19001_017E",
             ("cars", "none"): "B08201_002E",
             ("cars", "one"): "B08201_003E",
-            ("cars", "two or more"): "B08201_004E + B08201_005E + B08201_006E",
+            ("cars", "two or more"): "B08201_001E - (B08201_002E + B08201_003E)",
             ("workers", "none"): "B08202_002E",
             ("workers", "one"): "B08202_003E",
-            ("workers", "two or more"): "B08202_004E + B08202_005E"
+            ("workers", "two or more"): "B08201_001E - (B08202_002E + B08202_003E)"
         }, index_cols=['state', 'county', 'tract', 'block group'])
 
         population = ['B01001_001E']
diff --git a/synthpop/recipes/starter2.py b/synthpop/recipes/starter2.py
index 6d79d80..50dbe2d 100644
--- a/synthpop/recipes/starter2.py
+++ b/synthpop/recipes/starter2.py
@@ -105,10 +105,10 @@ def __init__(self, key, state, county, tract=None):
             ("hh_cars", "none"): "B08201_002E",
             ("hh_cars", "one"): "B08201_003E",
             ("hh_cars", "two or more"):
-                "B08201_004E + B08201_005E + B08201_006E",
+                "B08201_001E - (B08201_002E - B08201_003E)",
             ("hh_workers", "none"): "B08202_002E",
             ("hh_workers", "one"): "B08202_003E",
-            ("hh_workers", "two or more"): "B08202_004E + B08202_005E",
+            ("hh_workers", "two or more"): "B08202_001E - (B08202_002E - B08202_003E)",
             ("tenure_mover", "own recent"): "B25038_003E",
             ("tenure_mover", "own not recent"): "B25038_002E - B25038_003E",
             ("tenure_mover", "rent recent"): "B25038_010E",