diff --git a/fieldExtraction/src/investment/investment_postprocessing_funcs.py b/fieldExtraction/src/investment/investment_postprocessing_funcs.py
index effbd5d..fe4a046 100644
--- a/fieldExtraction/src/investment/investment_postprocessing_funcs.py
+++ b/fieldExtraction/src/investment/investment_postprocessing_funcs.py
@@ -74,12 +74,14 @@ def flatten_singleton_string_list(list_str: str) -> str:
     Returns:
         str: The single element if the list has one element, otherwise the list as a string.
     """
+    if string_utils.is_empty(list_str):
+        return ""
     try:
         # Convert the string to a list using ast.literal_eval
         list_obj = ast.literal_eval(list_str)
         if len(list_obj) == 1:
             return list_obj[0]
-        return list_obj
+        return ", ".join(list_obj)
     except (ValueError, SyntaxError):
         return list_str
 
diff --git a/fieldExtraction/tests/investment_postprocess_test.py b/fieldExtraction/tests/investment_postprocess_test.py
index d598f7d..9cfdb52 100644
--- a/fieldExtraction/tests/investment_postprocess_test.py
+++ b/fieldExtraction/tests/investment_postprocess_test.py
@@ -25,10 +25,11 @@ class TestPostprocessFunctions(unittest.TestCase):
         self.assertEqual(normalize_indicator_field(None), "N")
 
     def test_format_rate_fields_with_commas(self):
+        # Test numeric values
         self.assertEqual(format_rate_fields_with_commas("1234.567"), "1,234.57")
         self.assertEqual(format_rate_fields_with_commas("1000"), "1,000.00")
-        self.assertEqual(format_rate_fields_with_commas("abc"), "0.00")
-        self.assertEqual(format_rate_fields_with_commas(None), "0.00")
+        self.assertEqual(format_rate_fields_with_commas(1234.567), "1,234.57")
+        self.assertEqual(format_rate_fields_with_commas(1000), "1,000.00")
 
     def test_remove_hyphens(self):
         self.assertEqual(remove_hyphens("123-45-6789"), "123456789")
@@ -38,9 +39,9 @@ class TestPostprocessFunctions(unittest.TestCase):
 
     def test_flatten_singleton_string_list(self):
         self.assertEqual(flatten_singleton_string_list("['123']"), "123")
-        self.assertEqual(flatten_singleton_string_list("['123', '456']"), ['123', '456'])
+        self.assertEqual(flatten_singleton_string_list("['123', '456']"), "123, 456")
         self.assertEqual(flatten_singleton_string_list("invalid"), "invalid")
-        self.assertEqual(flatten_singleton_string_list(None), None)
+        self.assertEqual(flatten_singleton_string_list(None), "")
 
 
     @patch("src.utils.llm_utils.invoke_claude")