diff --git a/.gitignore b/.gitignore
index 920958e..dbf043a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,4 +10,6 @@
 .ipynb_checkpoints
 
 # Built Jupyter-Book documentation.
-docs/_build
\ No newline at end of file
+docs/_build
+
+.vscode/settings.json
diff --git a/docs/_toc.yml b/docs/_toc.yml
index 76d3734..d8c8318 100644
--- a/docs/_toc.yml
+++ b/docs/_toc.yml
@@ -1,10 +1,12 @@
-- file: home
+format: jb-article
+root: home
+sections:
 - file: examples
   sections:
-    - file: agg
-    - file: charts
-    - file: custom_taxes
-    - file: demo
-    - file: gini
-    - file: income_measures
-    - file: weighting
+  - file: agg
+  - file: charts
+  - file: custom_taxes
+  - file: demo
+  - file: gini
+  - file: income_measures
+  - file: weighting
diff --git a/microdf/__init__.py b/microdf/__init__.py
index 03d7165..3e9d327 100644
--- a/microdf/__init__.py
+++ b/microdf/__init__.py
@@ -44,6 +44,7 @@
     deep_poverty_rate,
     poverty_gap,
     squared_poverty_gap,
+    deep_poverty_gap,
 )
 from .style import AXIS_COLOR, DPI, GRID_COLOR, TITLE_COLOR, set_plot_style
 from .tax import mtr, tax_from_mtrs
@@ -132,6 +133,7 @@
     "deep_poverty_rate",
     "poverty_gap",
     "squared_poverty_gap",
+    "deep_poverty_gap",
     # style.py
     "AXIS_COLOR",
     "DPI",
diff --git a/microdf/generic.py b/microdf/generic.py
index b0906cf..a22e2b5 100644
--- a/microdf/generic.py
+++ b/microdf/generic.py
@@ -727,6 +727,22 @@ def poverty_gap(self, income: str, threshold: str) -> float:
         gaps = (threshold - income)[threshold > income]
         return gaps.sum()
 
+    @get_args_as_micro_series()
+    def deep_poverty_gap(self, income: str, threshold: str) -> float:
+        """Calculate deep poverty gap, i.e., the total gap between income and
+        half of poverty thresholds for all people in deep poverty.
+
+        :param income: Column indicating income.
+        :type income: str
+        :param threshold: Column indicating threshold.
+        :type threshold: str
+        :return: Deep poverty gap.
+        :rtype: float
+        """
+        deep_threshold = threshold / 2
+        gaps = (deep_threshold - income)[deep_threshold > income]
+        return gaps.sum()
+
     @get_args_as_micro_series()
     def squared_poverty_gap(self, income: str, threshold: str) -> float:
         """Calculate squared poverty gap, i.e., the total squared gap between
diff --git a/microdf/poverty.py b/microdf/poverty.py
index 6bc90f4..957ec0b 100644
--- a/microdf/poverty.py
+++ b/microdf/poverty.py
@@ -111,3 +111,27 @@ def squared_poverty_gap(
     if w is None:
         return sq_gap.sum()
     return (sq_gap * df[w]).sum()
+
+
+def deep_poverty_gap(
+    df: pd.DataFrame, income: str, threshold: str, w: str = None
+) -> float:
+    """Calculate deep poverty gap, i.e., the total gap between income and
+       halved poverty thresholds for all people in deep poverty.
+
+    :param df: DataFrame with income, threshold, and possibly weight columns
+        for each household (data should represent households, not persons).
+    :type df: pd.DataFrame
+    :param income: Column indicating income.
+    :type income: str
+    :param threshold: Column indicating threshold.
+    :type threshold: str
+    :param w: Column indicating weight, defaults to None (unweighted).
+    :type w: str, optional
+    :return: Deep poverty gap.
+    :rtype: float
+    """
+    gap = np.maximum((df[threshold] / 2) - df[income], 0)
+    if w is None:
+        return gap.sum()
+    return (gap * df[w]).sum()
diff --git a/microdf/tests/test_poverty.py b/microdf/tests/test_poverty.py
index f32ec20..68df0c9 100644
--- a/microdf/tests/test_poverty.py
+++ b/microdf/tests/test_poverty.py
@@ -53,7 +53,20 @@ def test_squared_poverty_gap():
     # Weighted
     RES = 1 * (25 ** 2) + 2 * (10 ** 2) + 3 * (5 ** 2)
     assert np.allclose(
-        mdf.squared_poverty_gap(df, "income", "threshold", "weight"),
-        RES,
+        mdf.squared_poverty_gap(df, "income", "threshold", "weight"), RES,
     )
     assert np.allclose(md.squared_poverty_gap("income", "threshold"), RES)
+
+
+def test_deep_poverty_gap():
+    # Unweighted
+    assert np.allclose(
+        mdf.deep_poverty_gap(df, "income", "threshold"), 17.5 + 5 + 0 + 0
+    )
+    # Weighted
+    RES = 17.5 * 1 + 5 * 2 + 0 * 3 + 0 * 4
+    assert np.allclose(
+        mdf.deep_poverty_gap(df, "income", "threshold", "weight"), RES
+    )
+    # Same in MicroDataFrame.
+    assert np.allclose(md.deep_poverty_gap("income", "threshold"), RES)