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- 2014-2-28
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- 1970-1-1
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写了个python程序计算了一下,看一下两种贷款的NPV哪个比较好:
def get_npv(self, yearly_risk_free_rate, yearly_mortgage_rate, terms_in_year, initial_loan):
monthly_mortgage_rate = yearly_mortgage_rate/12
terms_in_month = terms_in_year*12
monthly_payment = initial_loan*monthly_mortgage_rate*pow(1+monthly_mortgage_rate, terms_in_month)/(pow(1+monthly_mortgage_rate, terms_in_month)-1)
monthly_risk_free_rate = pow(1+yearly_risk_free_rate, 1/12)-1
npv = 0
for i in range(terms_in_month):
npv += monthly_payment/pow(1+monthly_risk_free_rate, i)
估算贷款100万,不考虑通货膨胀,不考虑未来大趋势变化:
//如果按照市场上无风险收益率,10年国债为标准(2%)左右:
//30年贷款
mortgage_analyzer.get_npv(yearly_risk_free_rate=0.02, yearly_mortgage_rate=0.0375, terms_in_year=30, initial_loan=-1000000)
NPV = -1258100.729869862
//15年贷款
mortgage_analyzer.get_npv(yearly_risk_free_rate=0.02, yearly_mortgage_rate=0.03, terms_in_year=15, initial_loan=-1000000)
NPV = -1076316.4615513163
所以,这种情况下,15年的还是划算的
//如果楼主对投资比较在行,收益率能比较高的话,比如能达到5.5%:
//30年贷款
mortgage_analyzer.get_npv(yearly_risk_free_rate=0.055, yearly_mortgage_rate=0.0375, terms_in_year=30, initial_loan=-1000000)
NPV = -831562.2844623666
//15年贷款
mortgage_analyzer.get_npv(yearly_risk_free_rate=0.055, yearly_mortgage_rate=0.03, terms_in_year=15, initial_loan=-1000000)
NPV = -856390.6726018086
这个时候,30年的开始明显划算
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不过,生活不是纯投资,要活的有幸福感,感觉30年的要舒服多了 |
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