diff --git a/nannyml/performance_calculation/calculator.py b/nannyml/performance_calculation/calculator.py
index ff05da7e..fb35a784 100644
--- a/nannyml/performance_calculation/calculator.py
+++ b/nannyml/performance_calculation/calculator.py
@@ -257,9 +257,6 @@ def __init__(
             for m in metrics
         ]
 
-        self.previous_reference_data: Optional[pd.DataFrame] = None
-        self.previous_reference_results: Optional[pd.DataFrame] = None
-
         self.result: Optional[Result] = None
 
     def __str__(self):  # noqa: D105
@@ -288,11 +285,9 @@ def _fit(self, reference_data: pd.DataFrame, *args, **kwargs) -> PerformanceCalc
                     f"an unexpected error occurred when calculating metric '{metric.display_name}': {exc}"
                 )
                 continue
-        self.previous_reference_data = reference_data
 
         self.result = self._calculate(reference_data)
         self.result.data[('chunk', 'period')] = 'reference'
-        self.result.reference_data = reference_data.copy()
 
         return self