The positive change in the index is a result, NAHB concludes, of the growing echo boomer population, as well as the increasing number of immigrants to the country. The multifamily business is, indeed, big business.

"Apartment stocks remain a darling for investors because they have offered attractive returns compared with other investment opportunities over the past five years," Elliot Eisenberg, an NAHB housing policy economist and MFSI developer, explains. "Despite the consistently strong showing of the S&P 500 over the past year, the MFSI has outperformed it. In fact, since December 1998 the MFSI has risen by 88%, while the S&P 500 with dividends reinvested has gained only one-half of 1%."