diff --git a/src/lib/Prop.re b/src/lib/Prop.re
index 768f9526..46f6dd17 100644
--- a/src/lib/Prop.re
+++ b/src/lib/Prop.re
@@ -1,14 +1,25 @@
 module Value = {
+  type binaryConditional =
+    | Selected(bool)
+    | Unselected;
   type t =
+    | BinaryConditional(binaryConditional)
     | SelectSingle(string)
     | DateTime(MomentRe.Moment.t)
     | FloatPoint(float)
+    | Probability(float)
     | FloatCdf(string);
 
   let to_string = (t: t) => {
     switch (t) {
+    | BinaryConditional(binaryConditional) =>
+      switch (binaryConditional) {
+      | Selected(r) => r ? "True" : "False"
+      | Unselected => ""
+      }
     | SelectSingle(r) => r
     | FloatCdf(r) => r
+    | Probability(r) => (r *. 100. |> Js.Float.toFixed) ++ "%"
     | DateTime(r) => r |> MomentRe.Moment.defaultFormat
     | FloatPoint(r) => r |> Js.Float.toFixed
     };
@@ -34,17 +45,23 @@ module Type = {
     max: option('a),
   };
 
+  type withDefault('a) = {default: option('a)};
+
   type t =
+    | BinaryConditional
     | SelectSingle(selectSingle)
     | FloatPoint(withDefaultMinMax(float))
+    | Probability(withDefault(float))
     | DateTime(withDefaultMinMax(MomentRe.Moment.t))
     | Year(withDefaultMinMax(float))
     | FloatCdf;
 
   let default = (t: t) =>
     switch (t) {
+    | BinaryConditional => Some(Value.BinaryConditional(Unselected))
     | Year(r) => r.default->Belt.Option.map(p => Value.FloatPoint(p))
     | FloatPoint(r) => r.default->Belt.Option.map(p => Value.FloatPoint(p))
+    | Probability(r) => r.default->Belt.Option.map(p => Value.Probability(p))
     | DateTime(r) => r.default->Belt.Option.map(p => Value.DateTime(p))
     | SelectSingle(r) =>
       r.default->Belt.Option.map(p => Value.SelectSingle(p))
diff --git a/src/lib/ValueForm.re b/src/lib/ValueForm.re
index b3983392..89a0e812 100644
--- a/src/lib/ValueForm.re
+++ b/src/lib/ValueForm.re
@@ -33,6 +33,36 @@ let make =
         }
       )}
     />
+  | (BinaryConditional, Some(BinaryConditional(r))) =>
+    switch (r) {
+    | Unselected =>
+      <div
+        onClick={_ => onChange(Some(BinaryConditional(Selected(true))))}>
+        {"Select" |> ReasonReact.string}
+      </div>
+    | Selected(true) =>
+      <div>
+        {"YES!" |> ReasonReact.string}
+        <div
+          onClick={_ => onChange(Some(BinaryConditional(Selected(false))))}>
+          {"No" |> ReasonReact.string}
+        </div>
+        <div onClick={_ => onChange(Some(BinaryConditional(Unselected)))}>
+          {"Deselect" |> ReasonReact.string}
+        </div>
+      </div>
+    | Selected(false) =>
+      <div>
+        {"NO!" |> ReasonReact.string}
+        <div
+          onClick={_ => onChange(Some(BinaryConditional(Selected(true))))}>
+          {"Yes" |> ReasonReact.string}
+        </div>
+        <div onClick={_ => onChange(Some(BinaryConditional(Unselected)))}>
+          {"Deselect" |> ReasonReact.string}
+        </div>
+      </div>
+    }
   | (Year(_), _)
   | (FloatPoint(_), _) => <input type_="number" value="" />
   | (SelectSingle(t), Some(SelectSingle(r))) =>
diff --git a/src/models/EAFunds.re b/src/models/EAFunds.re
index 368311d6..75b44750 100644
--- a/src/models/EAFunds.re
+++ b/src/models/EAFunds.re
@@ -11,8 +11,12 @@ module Data = {
 
   type output =
     | DONATIONS
+    | CHANCE_OF_EXISTENCE
     | PAYOUTS;
 
+  type conditionals =
+    | WORLD_CATASTROPHE;
+
   type fundWithInfo = {
     group,
     name: string,
@@ -93,6 +97,7 @@ module Model = {
     | (Fund(META), DONATIONS) => 9300000.0
     | (Fund(META), PAYOUTS) => 830000.0
     | (All, _) => sum()
+    | (_, CHANCE_OF_EXISTENCE) => 0.0
     };
   };
   let make =
@@ -102,14 +107,21 @@ module Model = {
         currentDateTime: MomentRe.Moment.t,
         output: output,
       ) => {
-    Prop.Value.FloatCdf(
-      calculateDifference(
-        currentValue(group, output),
-        dateTime,
-        currentDateTime,
-        yearlyMeanGrowthRateIfNotClosed(group),
-      ),
-    );
+    switch (output) {
+    | DONATIONS
+    | PAYOUTS =>
+      Prop.Value.FloatCdf(
+        calculateDifference(
+          currentValue(group, output),
+          dateTime,
+          currentDateTime,
+          yearlyMeanGrowthRateIfNotClosed(group),
+        ),
+      )
+    | CHANCE_OF_EXISTENCE =>
+      let yearDiff = MomentRe.diff(dateTime, currentDateTime, `days) /. 365.;
+      Prop.Value.Probability((100. -. yearDiff) /. 100.);
+    };
   };
 };
 
@@ -126,6 +138,7 @@ module Interface = {
   let outputFromString = (s: string) =>
     switch (s) {
     | "donations" => DONATIONS
+    | "exists" => CHANCE_OF_EXISTENCE
     | _ => PAYOUTS
     };
 
@@ -136,6 +149,7 @@ module Interface = {
         Some(DateTime(intendedYear)),
         Some(DateTime(currentYear)),
         Some(SelectSingle(output)),
+        Some(BinaryConditional(r)),
       |] =>
       choiceFromString(fund)
       |> E.O.fmap(fund =>
@@ -206,12 +220,19 @@ module Interface = {
             SelectSingle({
               default: Some("Output"),
               options: [
-                {name: "Donations", id: "donations"},
-                {name: "Funding", id: "funding"},
+                {name: "Donations | Exists", id: "donations"},
+                {name: "Funding | Exists", id: "funding"},
+                {name: "Exists", id: "exists"},
               ],
             }),
           (),
         ),
+        TypeWithMetadata.make(
+          ~name="Conditional on World Ending",
+          ~id="worldEnd",
+          ~type_=BinaryConditional,
+          (),
+        ),
       |],
       outputTypes: [||],
       run,