"significantly dropped" is a perfectly acceptable and common phrase in written English.
For example, you could say: "Sales of our product have significantly dropped this quarter."
Both EU and non-EU student enrolments have significantly dropped during 2013-2014.
Fran Shammo, Verizon's chief financial officer, also said new installations and orders had "significantly dropped".
At the same time, he said, sellers had not significantly dropped prices.
In the past few years, though, crime has significantly dropped, according to statistics compiled by the Port Authority.
As a result, the shares belonging to workers who had bought into the subsidiary in 1992 were watered down and significantly dropped in value.
Tourists come to see the birdlife, as the wetlands are one of Asia's most important sites for migratory birds, but the numbers of birds have significantly dropped in the last five years.
However, after two cycles, the oil recovery significantly dropped.
Google today significantly dropped the prices for its Google Drive online storage service.
Fatigue life significantly dropped for hold time fatigue tests in comparison with pure fatigue tests.
The SPR peak significantly dropped at pH 6, indicating a poor yield of AuNPs.
When analyzing by subgroup, headache frequency significantly dropped in all groups after randomization.
