By contrast, only about one-fourth of those people moving to a single-family detached home chose a central city location (see Table 1).

Interestingly, NAHB found that these percentages have been fairly stable since 1997 (Figure 1), which may be disappointing to people hoping for increased activity inner-city real estate markets and more infill development.

Source: American Housing Survey, U.S. Census Bureau and HUD

The only really notable change in the data is a spike in single-family detached activity in urban, non-metropolitan areas in 2005. This spike, which some observers would probably label an indicator of “sprawl,” is not present among those moving into either 5+ condos or rental apartments (Figure 2); however, a one-year spike needs to be viewed with caution, unless it persists for a while or is confirmed with other data.

Source: American Housing Survey, U.S. Census Bureau and HUD

Why are Multifamily Residents Choosing Central Cities?

Although the tendency to move into central cities indicates, to a certain extent, how dynamic the market is in those areas, it’s also a reflection of what’s available. Due to a number of inter-related reasons (such as high land costs, population density, and tradition), multifamily housing is more common in central cities than elsewhere. This begs the question of why multifamily residents choose to live in a particular location: Was it the only one available, or were they looking specifically for housing closer to their jobs and entertainment centers?

The AHS asks respondents both why they moved, and why they chose a particular neighborhood. ¹ Table 2 shows the reasons households give most often for moving.  The most common reason among households moving into 5+ rental apartments is to be closer to something (e.g. work or school). This contrasts with single-family detached households, for which the most common motivation is to get a larger house.

Table 3 shows the reasons households give most often for choosing a particular neighborhood. The reasons households in 5+ rental apartments cite most often is because the neighborhood is close to their jobs.  The “looks of the neighborhood,” although important to all three categories of recent movers, in the number one reason for both single-family detached households and 5+ condo households. Any reason that involves being close to something (job, family, leisure activities, public transportation), is far less often cited by single-family detached households than by  those moving into 5+ apartments. In 2005, the 5+ condo owners who recently moved cited being close to something as a reason for choosing a neighborhood a bit more often than the 5+ renters did. 

The only one of these tendencies that has changed much since 1997 is the relationship between movers into 5+ rental apartments and 5+ condos. The share choosing a neighborhood because it was close to work has generally hovered around 40% for both 5+ renter and condo households, but only around 25% for those in single family-detached homes (Figure 3).

Source: American Housing Survey, U.S. Census Bureau and HUD

It’s important to remember that number of households moving into 5+ condos in a given year is small compared to the number moving into either 5+ rental or single-family detached housing, so sampling error is likely to have greater impact and there’s likely to be more year-to-year volatility in the 5+ condo numbers.

The spread among household types choosing a neighborhood because it’s close to friends or family is smaller; but in every year of the AHS since 1997, movers into single-family detached homes still cited this reason less often than movers into 5+ units did (Figure 4).

As in several of these figures, there’s a spike in 1999 for movers into 5+ condos. Again, it’s advisable to keep the small sample size for this segment of the market in mind.

The 5+ condo households are particularly likely to choose a neighborhood because it’s close to leisure activities, especially after 1997 (Figure 5). The spread between 5+ renters and single-family detached households is quite narrow, but the share for 5+ renters is slightly higher throughout the graph. 

Source: American Housing Survey, U.S. Census Bureau and HUD

About 13% to 14% of households moving into 5+ rental apartments consistently choose a neighborhood in order to be close to public transportation (Figure 6). The share among movers into 5+ condos is slightly higher, ranging from 13% to a perhaps anomalous spike of 20% in 1999.

Source: American Housing Survey, U.S. Census Bureau and HUD

These percentages, consistently lower than those for choosing a neighborhood to be close to a job or family or leisure activities, may seem discouraging to advocates of public transportation. But they are much higher for 5+ households than for households moving into single-family detached units—only 3% of whom reported choosing a neighborhood to be close to public transportation in 2005.

A Look at Traffic Generated

If households moving into multifamily structures are choosing neighborhoods in order to be close to things, this should show up in several related statistics. One is the amount of traffic generated per unit.

NAHB looked at  Trip Generation, published by the Institute of Transportation Engineers for some additional insight on this topic. The 7th edition of Trip Generation, published in 2003, compiles data from over 4,000 transportation studies conducted by public agencies, developers, consulting firms, and associations. Data shown include the average number of trips (vehicles entering or leaving a site) per day and, during peak travel times, per hour. Statistics are provided for a variety of land uses, including several categories of multifamily housing.

The data clearly show that, compared to a single-family home, an average multifamily unit generates fewer trips (Table 4).

For example, on weekdays a single-family detached home generates 9.57 trips, compared to 6.72 for a rental apartment, and only 4.20 for an apartment in a high-rise (more than 10-story) building.   

The statistic that should be of greatest interest to city planners and those trying to persuade city planners that multifamily housing benefits communities is the number of trips generated during rush hours. These are the times when local streets are most congested, and the peak traffic load is what streets need to be designed to handle. Here again, the numbers are lower for multifamily than for single-family housing.  While a single-family home generates 1.01 trips per evening rush hour (peak hour of street traffic between 4 and 6 P.M. on weekdays), an average rental apartment generates only 0.62, and an average high-rise apartment only 0.35 (figure 7). 

Source: American Housing Survey, U.S. Census Bureau and HUD

Trip Generation also contains information about condominiums (and includes townhouses in this category). In general, average trip figures per unit are slightly lower for condominiums than they are for rental apartments, if height of the building is not taken into account. Low rise-condos generate more trips than low-rise rental apartments during morning and evening rush hours. On weekdays, the trip generation figures for high-rise condos and high-rise rental apartments are similar. Where data are available, the average number of trips generated by condos with luxury features or services is very similar to the corresponding number for rental apartments (the luxury condo studies compiled in Trip Generation do not in general define what constitutes a luxury feature or service). As with rental apartments, all categories of condos generate fewer vehicle trips than single-family units, and this is true on weekdays and weekends, as well as during peak traffic hours.

The Impact of Multifamily Households on Commuting

Although the information on traffic generated is interesting and useful, it doesn’t, by itself, demonstrate that multifamily residents are exhibiting any special behavioral traits that reduce traffic. Multifamily households tend to be smaller, and will generate fewer trips per unit for that reason alone. Multifamily housing also is by its nature more dense, so an equivalent number of trips generated per acre can be generated with single-family and multifamily development, since fewer trips per unit may be offset by more units per acre. (On the other hand, multifamily is one way to cluster residential units together, leaving more contiguous open space in the community for a given number of housing units, and many would see this as an advantage.)

If individuals who move into multifamily housing are choosing their locations to be close to work or public transportation, this should result in household heads having shorter commutes to work and using public transportation more often to get to there. This type of information is also contained in the AHS (Table 5). 

On average, households moving into 5+ multifamily rental units own only about half as many vehicles as households moving into single family units (a little over one per household vs. a little over two). This is another statistic that’s related to household size, so the table also shows the share of household heads who use their cars to drive to work. Roughly 80% of movers into 5+ rental apartments and 5+ condos drive to work. This may seem high, but the share for households moving into single-family detached homes is more than 90%, and this has not changed at all since 1997 (Figure 8). 

Source: American Housing Survey, U.S. Census Bureau and HUD

In terms of increased use of public transportation, these results are not encouraging. Driving remains the dominant way of traveling to work, and streets and the highways needed to support commuting are designed with this in mind. To the extent that there is a tendency to use public transportation (bus, subway, rail) to get to work, it is much stronger among household heads who move into 5+ rental units (9.7%) and especially 5+ condos (15.9%) than into single-family detached units (1.4%). A few movers into 5+ structures also walk to work, while the share among movers into single-family detached housing is almost negligible.

Household heads who recently moved into 5+ structures also have shorter distances to work, and take less time getting there. In some cases, these tendencies show up more strongly at the top end of the distribution (say, at the 90th percentile) than in the middle (represented by the median). ² For example, Table 5 shows that 10% of movers into 5+ rental apartments and condos travel at least 25 miles to get to work, while 10% of movers into single-family detached homes travel at least 45 miles. Similarly, it takes 10% of movers into 5+ rental apartments and condos at least 45 minutes to get to work, but the commute for the top 10% of movers into single family detached takes at least an hour. 

Conclusion

Throughout the 1997-2005 period, the people who moved into multifamily units tended to be those looking for places to live that are close to jobs, family, friends and leisure-time activities. Related statistics show that, compared to their single- family counterparts, multifamily households own fewer vehicles and generate less traffic per housing unit, although this is at least partly a function of smaller household size. Multifamily household heads are more likely to use public transportation and to have shorter and quicker commutes to work, however, which is consistent with survey responses indicating that this often why they chose to move in general, and to move into particular neighborhoods.

When approaching city planners who are trying to increase the use of public transportation, to locate housing and work places close to each other, and generally ease congestion on neighborhood streets, devleopers should call attention to these tendencies of people who move into multifamily buildings. This doesn’t imply that cities should try to build nothing but multifamily housing. A substantial share of the population seems to prefer living in single-family detached structures, and local planning decisions are unlikely to change this drastically. The housing mix in a community needs to match the mix demanded by its local residents. However, to the extent that, at the margins, it’s possible to attract multifamily residents into an area, it means attracting residents who tend to be looking for places to live near where they work and who are somewhat more inclined to use public transportation—something that can only happen if the local housing stock includes a reasonable share of multifamily units.  Planners’ perception of multifamily development should be broad enough to encompass the relatively favorable commuting behavior of the people who tend to move into it.

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¹ The AHS asks the questions in two forms: 1) what was the main reason, and 2) what were all reasons.  This article shows just answers to questions in the second form.  The percentages are higher and therefore somewhat easier to discuss.  It’s possible to tell essentially the same story based on either set of responses.
² The 90th percentile is value (in miles or minutes) for which 90 percent of the people in the group have shorter commutes and 10 percent have longer commutes.  The median is the value that cuts the sample in half.  Fifty percent of the people have shorter commutes, and 50 percent have longer commutes than the median.  
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