The paper studies the impact of the EP on legislation on chemical pollutant
s introduced under the Cooperation procedure. A series of formal and inform
al analyses have predicted from significant impact of the EP, to limited im
pact (only in the second round) to no impact at all. Through the analysis o
f Parliamentary debates as well as Commission and Parliamentary committee d
ocuments, we are able to assess the significance of different amendments, a
s well as the degree to which they were introduced in the final decision of
the Council. Our analysis indicates first that less than 30% of EP amendme
nts are insignificant, while 15% are important or very important; second, t
hat the probability of acceptance of an amendment is the same regardless of
its significance. Further analysis indicates two sources of bias of aggreg
ate EP statistics: several amendments are complementary (deal with the same
issue in different places of the legal document), and a series of amendmen
ts that are rejected as inadmissible (because they violate the legal basis
of the document or the germainess requirement) are included in subsequent p
ieces of legislation. We calculate the effect of these biases in our sample
, and find that official statistics underestimate Parliamentary influence b
y more than 6 percentage points (49% instead of 56% in our sample). Finally
, we compare a series of observed strategic behaviors of different actors (
rapporteurs, committees, floor, Commission) to different expectations gener
ated by the literature.