Question results in "DriverImportance" = 1 everywhere

[halirutan]

The following question returns a dataset where all "DriverImportance" values seem to be 1:

Find the 10 most frequent driver chemicals above a driver importance of 0.6

The CypherQAChain uses the following query

cypher
MATCH (s:Substance)-[r:IS_DRIVER]->(l:Site)
WHERE r.driver_importance > 0.6
RETURN s.name AS ChemicalName, // plot title
r.driver_importance AS DriverImportance, // [0,1], continuous point color from blue to red, with midpoint at 0.5
l.name AS SiteName, // point hover
l.water_body AS WaterBody, l.river_basin AS RiverBasin, // point hover
l.lat AS Lat, l.lon AS Lon // x,y coordinates
ORDER BY r.driver_importance DESC
LIMIT 10

[mai00fti]

This is a correct result for this question.
A driver_importance of 1 indicates that there is a single substance explaining the total risk for a certain species at the site.
The term for these substances is "single risk driver".

Substances with driver_importance below 1 but above 0.4 (empirical value) are those that contribute only partially to the total risk observed at a site for a given species.
The term for those is "mixture risk drivers".

There are 88 substances with driver_importance=1 distributed across 1208 sites resulting in 5475 records that will be returned by this query.

To avoid confusion here, we may think of an alternative questions.
Suggestions:

1. Which substances are most frequently observed as single risk drivers?
2. Which substances are most frequently observed as mixture risk drivers?

I will rethink this example and provide appropriate questions and cypher queries asap.