As applied to the behavior of homeowners with mortgages, option theory predicts that mortgage prepayment or default will be exercised if the call or put option is ''in the money'' by some specific amount. Our analysis: tests the extent to which the option approach can explain default and prepayment behavior; evaluates the practical importance of modeling both options simultaneously; and models the unobserved heterogeneity of borrowers in the home mortgage market. The paper presents a unified model of the competing risks of mortgage termination by prepayment and default, considering the two hazards as dependent competing risks that are estimated jointly. It also accounts for the unobserved heterogeneity among borrowers, and estimates the unobserved heterogeneity simultaneously with the parameters and baseline hazards associated with prepayment and default functions.Our results show that the option model, in its most straightforward version, does a good job of explaining default and prepayment, but it is not enough by itself. The simultaneity of the options is very important empirically in explaining behavior. The results also show that there exists significant heterogeneity among mortgage borrowers. Ignoring this heterogeneity results in serious errors in estimating the prepayment behavior of homeowners.

Injury to a peripheral nerve induces in the dorsal root ganglia (DRG) sprouting of sympathetic and peptidergic terminals around large-diameter sensory neurons that project in the damaged nerve. This pathological change may be implicated in the chronic pain syndromes seen in some patients with peripheral nerve injury. The mechanisms underlying the sprouting are not known. Using in situ hybridization and immunohistochemical techniques, we have now found that nerve growth factor (NGF) and neurotrophin-3 (NT3) synthesis is upregulated in satellite cells surrounding neurons in lesioned DRG as early as 48 h after nerve injury. This response lasts for at least 2 months. Quantitative analysis showed that the levels of mRNAs for NT3 and NGF increased in ipsilateral but not contralateral DRG after nerve injury. Noradrenergic sprouting around the axotomized neurons was associated with p75-immunoreactive satellite cells. Further, antibodies specific to NGF or NT3, delivered by an osmotic mini-pump to the DRG via the lesioned L5 spinal nerve, significantly reduced noradrenergic sprouting. These results implicate satellite cell-derived neurotrophins in the induction of sympathetic sprouting following peripheral nerve injury.

High and rising prices in Chinese housing markets have attracted global attention, as well as the interest of the Chinese government and its regulators. Housing markets look very risky based on the stylized facts we document. Price-to-rent ratios in Beijing and seven other large markets across the country have increased from 30% to 70% since the beginning of 2007. Current price-to-rent ratios imply very low user costs of no more than 2%-3% of house value. Very high expected capital gains appear necessary to justify such low user costs of owning. Our calculations suggest that even modest declines in expected appreciation would lead to large price declines of over 40% in markets such as Beijing, absent offsetting rent increases or other countervailing factors. Price-to-income ratios also are at their highest levels ever in Beijing and select other markets. Much of the increase in prices is occurring in land values. Using data from the local land auction market in Beijing, we are able to produce a constant quality land price index for that city. Real, constant quality land values have increased by nearly 800% since the first quarter of 2003, with half that rise occurring over the past two years. State-owned enterprises controlled by the central government have played an important role in this increase, as our analysis shows they paid 27% more than other bidders for an otherwise equivalent land parcel.

As applied to the behavior of homeowners with mortgages, option theory predicts that mortgage prepayment or default will be exercised if the call or put option is ''in the money'' by some specific amount. Our analysis: tests the extent to which the option approach can explain default and prepayment behavior; evaluates the practical importance of modeling both options simultaneously; and models the unobserved heterogeneity of borrowers in the home mortgage market. The paper presents a unified model of the competing risks of mortgage termination by prepayment and default, considering the two hazards as dependent competing risks that are estimated jointly. It also accounts for the unobserved heterogeneity among borrowers, and estimates the unobserved heterogeneity simultaneously with the parameters and baseline hazards associated with prepayment and default functions.Our results show that the option model, in its most straightforward version, does a good job of explaining default and prepayment, but it is not enough by itself. The simultaneity of the options is very important empirically in explaining behavior. The results also show that there exists significant heterogeneity among mortgage borrowers. Ignoring this heterogeneity results in serious errors in estimating the prepayment behavior of homeowners.

In generating fast economic growth, China is also generating growing concern about its environmental record. Using 2000-2009 data, we find that, while spending on environmental infrastructure has visible positive environmental impact, city spending is strongly tilted towards transportation infrastructure. Investment in transportation infrastructure correlates strongly with both real GDP growth, a measure of tangible economic growth relevant to city-level Party and government cadres' promotion odds, and with land prices, which affect city governments' revenues from land lease sales. In contrast, city governments' spending on environmental improvements is at best uncorrelated with cadres' promotion odds, and is uncorrelated with local GDP growth and land prices. These findings suggest that, were environmental quality explicitly linked to a cadre's chance of promotion, or were environmental quality to affect land prices substantially, city-level public investment in environmental improvement would rise.

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High and rising prices in Chinese housing markets have attracted global attention, as well as the interest of the Chinese government and its regulators. Housing markets look very risky based on the stylized facts we document. Price-to-rent ratios in Beijing and seven other large markets across the country have increased from 30% to 70% since the beginning of 2007. Current price-to-rent ratios imply very low user costs of no more than 2%-3% of house value. Very high expected capital gains appear necessary to justify such low user costs of owning. Our calculations suggest that even modest declines in expected appreciation would lead to large price declines of over 40% in markets such as Beijing, absent offsetting rent increases or other countervailing factors. Price-to-income ratios also are at their highest levels ever in Beijing and select other markets. Much of the increase in prices is occurring in land values. Using data from the local land auction market in Beijing, we are able to produce a constant quality land price index for that city. Real, constant quality land values have increased by nearly 800% since the first quarter of 2003, with half that rise occurring over the past two years. State-owned enterprises controlled by the central government have played an important role in this increase, as our analysis shows they paid 27% more than other bidders for an otherwise equivalent land parcel.