This study is useless. All it can tell us is: The number of insects flying above two particular roadways in one country over the course of 2 decades has decline

This study is useless. All it can tell us is: The number of insects flying above two particular roadways in one country over the course of 2 decades has declined by about 90%. We can wildly speculate about what this means. Is it genetically-modified crops? Is it climate change? Is it changes to our automobiles? Is it population density changes? Are the bugs increasing elsewhere to compensate? etc. Has something about roads in Denmark changed? Is this part of a larger cycle within Denmark?