NBER Publications by Massimo Massa

We relate the degree of investor portfolio focus to the broader urban economic context of the household. Using a detailed panel of investors in Sweden over the period 1995 to 2000, we find that the level of investor diversification, as measured by number of stocks in the portfolio and by the average correlation among holdings, is partially explained by city industrial characteristics. We find that rural portfolios are more diversified than urban portfolios and that portfolio diversification is characterized by factors associated with urban growth. We consider a number of theories to explain investor focus, including behavioral biases, real and perceived informational advantage, local social competition and hedging of non-tradable risk. We find little evidence to support social and hedging ...

In this paper, we estimate the behavioral component of the Grinblatt and Han (2002) model and derive several testable implications about the expected relationship between the preponderance of disposition-prone investors in a market and volume, volatility and stock returns. To do this, we use a large sample of individual accounts over a six-year period in the 1990's in order to identify investors who are subject to the disposition effect. We then use their trading behavior to construct behavioral factors. We show that when the fraction of irrational' investor purchases in a stock increases, the unexplained portion of the market price of the stock decreases. We further show that statistical exposure to a disposition factor explains cross-sectional differences in daily returns, controlling fo...

We use a two-year panel of individual accounts in an S&P 500 index mutual fund to examine the trading and investment behavior of more than 91 thousand investors who have chosen a low-cost, passively managed vehicle for savings. This allows us to characterize investors' heterogeneity in terms of their investment patterns. In particular, we identify positive feedback traders as well as contrarians whose activities are conditional upon preceding day stock market moves. We test the consistency and profitability of these conditional strategies over time. We find that more frequent traders are typically contrarians, while infrequent traders are more typically momentum investors. The dynamics of these investor classes help us to partially examine the question of the marginal investor over the pe...

In the present paper we analyze the relationship between index funds and asset prices. In particular, our analysis of daily index fund flows indicates a strong contemporaneous correlation between fund inflows and S&P market returns. We also document a strong negative correlation between fund out flows and S&P market returns with the exception of outflows from a fund with very high initial investment requirement. These effects may be interpreted in two ways. Either investor supply and demand affects S&P market prices, or investors condition their demand and supply on intra-day market fluctuations. To sort out these effects, we examine trailing investor reaction to market moves. Our results suggest the market reacts to daily demand. However, only negative reactions appear due to past returns...