As of April 2014, there are 88 private schools in New Zealand, catering for around 28,000 students or 3.7% of the entire student population. Private school numbers have been in decline since the mid-1970s as a result of many private schools opting to become state-integrated schools, mostly due of financial difficulties stemming from changes in student numbers and/or the economy. State-integrated schools keep their private school special character and receives state funds in return for having to operate like a state school, e.g. they must teach the state curriculum, they must employ registered teachers, and they can't charge tuition fees (they can charge "attendance dues" for the upkeep on the still-private school land and buildings). The largest decline in private school numbers occurred between 1979 and 1984, when the nation's then-private Catholic school system integrated. As a result, private schools in New Zealand are now largely restricted to the largest cities (Auckland, Hamilton, Wellington and Christchurch) and niche markets.