diff --git a/src/ILAMB/ConfRatio.py b/src/ILAMB/ConfRatio.py
new file mode 100644
index 00000000..72e14543
--- /dev/null
+++ b/src/ILAMB/ConfRatio.py
@@ -0,0 +1,91 @@
+"""."""
+import os
+
+import numpy as np
+
+from . import ilamblib as il
+from .Confrontation import Confrontation
+from .Variable import Variable
+
+
+def variable_ratio(num: Variable, den: Variable):
+    """."""
+    den.convert(num.unit)
+    years = np.asarray([num.time_bnds[::12, 0], num.time_bnds[11::12, 1]]).T
+    num = num.coarsenInTime(years)
+    den = den.coarsenInTime(years)
+    with np.errstate(under="ignore"):
+        ratio = num.data / den.data
+    ratio = Variable(
+        name="ratio",
+        unit="1",
+        data=ratio,
+        time=num.time,
+        time_bnds=num.time_bnds,
+        lat=num.lat,
+        lat_bnds=num.lat_bnds,
+        lon=num.lon,
+        lon_bnds=num.lon_bnds,
+    )
+    return ratio
+
+
+class ConfRatio(Confrontation):
+    """.
+    * over_regions, a list of regions overwhich to compute averages, could be basins here
+    * mask_lower_percentile = 0.05, would create a mask of the lower end of the denominator and intepolate the mask to the model
+    """
+
+    def __init__(self, **keywords):
+        required_keys = [
+            "numerator_source",
+            "numerator_variable",
+            "denominator_source",
+            "denominator_variable",
+        ]
+        if set(required_keys).difference(keywords):
+            msg = f"This confrontation requires a different set of keywords: {','.join(required_keys)}"
+            raise il.MisplacedData(msg)
+        for key in ["numerator_source", "denominator_source"]:
+            keywords[key] = os.path.join(os.environ["ILAMB_ROOT"], keywords[key])
+        keywords["source"] = keywords["numerator_source"]
+        keywords["skip_cycle"] = True
+        keywords["skip_sd"] = True
+        keywords["rmse_score_basis"] = "series"
+        self.source = keywords["numerator_source"]
+        super().__init__(**keywords)
+
+    def stageData(self, m):
+        """."""
+        # construct observation ratios
+        kwargs = self.keywords
+        num = Variable(
+            filename=kwargs["numerator_source"],
+            variable_name=kwargs["numerator_variable"],
+        )
+        den = Variable(
+            filename=kwargs["denominator_source"],
+            variable_name=kwargs["denominator_variable"],
+            t0=num.time_bnds.min(),
+            tf=num.time_bnds.max(),
+        )
+        num.trim(t=[den.time_bnds.min(), den.time_bnds.max()])
+        obs = variable_ratio(num, den)
+
+        # constructor model ratios
+        num = m.extractTimeSeries(
+            kwargs["numerator_variable"],
+            initial_time=obs.time_bnds[0, 0],
+            final_time=obs.time_bnds[-1, 1],
+            lats=None if obs.spatial else obs.lat,
+            lons=None if obs.spatial else obs.lon,
+        )
+        den = m.extractTimeSeries(
+            kwargs["denominator_variable"],
+            initial_time=obs.time_bnds[0, 0],
+            final_time=obs.time_bnds[-1, 1],
+            lats=None if obs.spatial else obs.lat,
+            lons=None if obs.spatial else obs.lon,
+        )
+        mod = variable_ratio(num, den)
+        return obs, mod
diff --git a/src/ILAMB/Scoreboard.py b/src/ILAMB/Scoreboard.py
index 5cdb3f3c..192a0500 100644
--- a/src/ILAMB/Scoreboard.py
+++ b/src/ILAMB/Scoreboard.py
@@ -13,6 +13,7 @@
 from .ConfSoilCarbon import ConfSoilCarbon
 from .ConfUncertainty import ConfUncertainty
 from .ConfBurntArea import ConfBurntArea
+from .ConfRatio import ConfRatio
 try:
     from .ConfUSGS import ConfUSGS
 except:
@@ -328,7 +329,8 @@ def _loadScores(node):
                        "ConfSoilCarbon"  : ConfSoilCarbon,
                        "ConfUncertainty" : ConfUncertainty,
                        "ConfBurntArea"   : ConfBurntArea,
-                       "ConfUSGS"        : ConfUSGS }
+                       "ConfUSGS"        : ConfUSGS,
+                       "ConfRatio"       : ConfRatio }
 
 class Scoreboard():
     """