diff --git a/sharkfin/tests/test_simulation.py b/sharkfin/tests/test_simulation.py
index 2457cde..b6a9207 100644
--- a/sharkfin/tests/test_simulation.py
+++ b/sharkfin/tests/test_simulation.py
@@ -95,7 +95,6 @@ def test_macro_simulation():
         SequentialPortfolioConsumerType,
         WHITESHARK,
         rng=np.random.default_rng(1),
-        num_per_type=2,
     )
 
     # arguments to attention simulation
@@ -143,7 +142,6 @@ def test_attention_simulation():
         SequentialPortfolioConsumerType,
         WHITESHARK,
         rng=np.random.default_rng(1),
-        num_per_type=2,
     )
 
     # arguments to attention simulation
@@ -205,7 +203,6 @@ def test_lucas0_simulation():
         SequentialPortfolioConsumerType,
         LUCAS0,
         rng=np.random.default_rng(1),
-        num_per_type=100,
     )
 
     # arguments to attention simulation
diff --git a/simulate/parameters.py b/simulate/parameters.py
index 97bb206..b97f88b 100644
--- a/simulate/parameters.py
+++ b/simulate/parameters.py
@@ -7,7 +7,10 @@
 from sharkfin.population import AgentPopulation
 
 
-def build_population(agent_type, parameters, num_per_type=1, rng=None, dphm=1500):
+def build_population(agent_type, parameters, rng=None, dphm=1500):
+
+    num_per_type = parameters.pop("num_per_type", 1)
+
     pop = AgentPopulation(
         agent_type(), parameters, rng=rng, dollars_per_hark_money_unit=dphm
     )
@@ -101,6 +104,6 @@ def build_population(agent_type, parameters, num_per_type=1, rng=None, dphm=1500
 
 lucas0_parameter_dict = lucas0_agent_population_params
 lucas0_parameter_dict["AgentCount"] = 10  # TODO: What should this be?
-
+lucas0_agent_population_params["num_per_type"] = 10
 
 LUCAS0 = lucas0_parameter_dict