I remember reading a story years ago concerning India and its problem of overpopulation - they were trying to bribe men into having vasectomies. The most successful incentive seemed to be offering a transistor radio.
Japan too is experiencing negative population growth - many professional couples are delaying parenthood, or choosing not to procreate. As I remember, Japan's government is increasing immigration quotas as a response.
In your case, I wonder if anyone has crunched the numbers: the size of the fine versus what it would cost to give birth and raise a child? I think in most societies, 5% of a salary is far less than the cost of parenthood.