diff --git a/src/fairness.jl b/src/fairness.jl
index 90c80ce..a99ec0c 100644
--- a/src/fairness.jl
+++ b/src/fairness.jl
@@ -67,7 +67,7 @@ module Fairness
         end
     end
 
-    function _demographic_parity(cohorts, funcs, conn, reference_subjects, process_size, silver)
+    function _demographic_parity(cohorts::Vector{<:Any}, funcs, conn, reference_subjects, process_size, silver)
 
         _funcs = [Fix2(fun, conn) for fun in funcs]
 
@@ -128,7 +128,7 @@ module Fairness
         return dps
     end
 
-    function _demographic_parity(cohorts, funcs, conn, reference_subjects, process_size)
+    function _demographic_parity(cohorts::Vector{<:Any}, funcs, conn, reference_subjects, process_size)
 
         _funcs = [Fix2(fun, conn) for fun in funcs]
 
@@ -167,6 +167,45 @@ module Fairness
         return dps
     end
 
+    function _demographic_parity(cohorts::DataFrame, funcs, conn, reference_subjects, process_size)
+
+        _funcs = [Fix2(fun, conn) for fun in funcs]
+
+        if isempty(reference_subjects)
+            reference_subjects = GetDatabasePersonIDs(conn)
+        end
+
+        cohorts = cohorts.subject_id
+
+        subsets = _subset_subjects(reference_subjects, process_size)
+
+        denom = DataFrame()
+        for sub in subsets
+            denom = vcat(denom, _counter_reducer(sub, :count_denom, _funcs))
+        end
+
+        denom = groupby(denom, names(denom)[1:end-1]) |> 
+        x -> combine(x, :count_denom => sum => :count_denom)
+
+        subsets = _subset_subjects(cohorts, process_size)
+
+        num = DataFrame()
+        for sub in subsets
+            num = vcat(num, _counter_reducer(sub, :count_num, _funcs))
+        end
+
+        num = groupby(num, names(num)[1:end-1]) |> 
+        x -> combine(x, :count_num => sum => :count_num)
+
+        dps = outerjoin(num, denom; on = names(num)[1:end-1] .|> 
+        x -> Symbol(x) => Symbol(x)) |>
+        x -> coalesce.(x, 0)
+
+        dps.demographic_parity = dps.count_num ./ dps.count_denom
+
+        return dps
+    end
+
     function equality_of_opportunity(cohorts, funcs, conn; reference_subjects = "", process_size = 10000)
 
         _funcs = [Fix2(fun, conn) for fun in funcs]