Is it always man's responsibility to run the house? Does wife has to contribute in case where she has a job? What is the situation where husband is jobless and wife is working? What is Islamic ruling about this.
The wife CANNOT BE FORCED to pay a penny. It's totally a man's duty. If he has a shortage, then he is forced to decrease THEIR standard of living, this does not give him the right to ask his wife to share the pay.
The wife can, of course, help her husband any time favourably.
Many evidences are included in this arabic fatwa.