Table of Contents
Key Insights
- Naturally occurring affordable housing (NOAH) is unsubsidized rental housing that stays affordable through market dynamics alone, not public subsidy. It’s a critical source of affordable housing but has historically been difficult to measure.
- In collaboration with LACAHSA, NDSC developed a novel classification scheme for NOAH, based on building age and size, to overcome the data limitations of prior approaches like income-based measures.
- Our NOAH definition identifies three affordability tiers: Core (built before 2000, 5-19 units), Expanded (pre-2000, 20-49 units), and Marginal (pre-2000, 50-99 units). Together they total nearly 809,000 units countywide. The Core NOAH units are nearly 43% (460,000 units) of the county’s multifamily rental stock with 5+ units and about a quarter of the county’s total rental stock.
- Renter-level data validate the scheme. Self-reported rents follow the predicted NOAH tier gradient and also show that NOAH residents are diverse, often long-tenured, and disproportionately low-income when compared to residents of other market-rate units.
- Hollywood-Studio City stands out geographically, with both the largest total NOAH stock (approximately 155,000 units) and the second-highest concentration (61% of its rental units).
- Given the time and expense that constructing subsidized housing entails, preserving the NOAH stock is essential to preventing further erosion in the county’s affordability.
Naturally Occurring Affordable Housing in Los Angeles County
Naturally occurring affordable housing, or NOAH, refers to unsubsidized housing that remains affordable to lower-income households through market dynamics rather than through formal public subsidies. In the County of Los Angeles, this stock matters because it constitutes a majority of units that are affordable to local families, particularly in certain areas of the county. Yet these units are often less easily tracked than income-restricted or program-based affordable housing, creating challenges to developing and executing interventions aimed at preserving NOAH units.
This chapter outlines the methodology the team has developed to estimate this aging, but critical, piece of Los Angeles County’s housing supply. It also examines how these estimates vary across regions of the county, and the characteristics of renter households that are typically living in NOAH units.
What counts as NOAH?
The total number of NOAH units in a given market or submarket equals the number of rental units affordable to lower-income households minus the number of subsidized rental housing units.
Subtracting out subsidized units is critical because some units may appear affordable based on rents but are affordable only because they are supported by federal, state, or local subsidy programs; if we do not remove those units, we overestimate NOAH.1
Although the definition of NOAH may seem straightforward at first glance, counting the total number of rental units that are affordable to lower-income households is complicated. First, there is no consensus on which households are deemed lower-income and what rents are affordable to them. Variation in these definitions has yielded different estimates of the total NOAH stock. Second, there is no comprehensive dataset reporting rents for all rental units on the market. Third, relying on survey data (e.g., from the American Community Survey) on self-reported rents and household incomes may generate estimates that are contaminated by measurement error and that systematically underestimate rent levels if the units were put on the open market (i.e., due to rent stabilization laws and to landlords’ tendency to charge longer-term tenants lower rents) (Barker, 2003; Guasch & Marshall, 1987). Fourth, in order to protect respondent privacy, survey data typically only provide information on rents and incomes at large spatial scales (e.g., the public use microdata data areas, which encompass over 100,000 residents), precluding identification of specific parcels where NOAH units may be located.
To overcome these limitations, we opt for a property characteristics approach to estimate the number of NOAH units in LA County, based on buildings’ observable characteristics – specifically the age and size of buildings containing rental housing units – tracked in parcel-level datasets. Existing research suggests older and smaller multifamily buildings with rental housing tend to command lower rents compared to newer and larger ones, indicating they could be considered affordable relative to local rental housing costs (Song & Reid, 2026).
An NDSC definition of NOAH in LA County
In partnership with the Los Angeles County Affordable Housing Solutions Agency, NDSC defines NOAH in LA County as older multifamily rental housing units, using three categories of building age and size to capture variation in affordability:
- Core NOAH (most affordable older multifamily rental housing) includes buildings built before 2000 with 5-19 units.
- Expanded NOAH includes buildings built before 2000 with 20-49 units.
- Marginal NOAH (least affordable older multifamily rental housing) includes buildings built before 2000 with 50-99 units.
We use this three-category definition because it fits Los Angeles County’s housing market better than a one-size-fits-all rule: In our parcel-level dataset of the universe of LA County properties of 5+ units, rents rise more sharply for properties built after 2000, and within the older stock, smaller buildings tend to charge lower rents than larger ones. The chart below shows size-adjusted monthly rent by construction decade and building size, revealing both patterns clearly (see Data & Methods page for details about the analytic dataset and how we calculate the size-adjusted monthly rent).
Note: To standardize rents across properties, we multiplied each property’s average asking rent per square foot by 700 to approximate the monthly rent for a one-bedroom apartment. For more detailed information, please visit the Data & Methods page.
The definition’s simplicity is also a key benefit. Rather than relying on institutional ownership categories (e.g., mom-and-pop vs. large corporate landlord) that can be difficult to track accurately and consistently, we focus on two features that are widely available in property records collected by Assessors’ offices: when the building was built and how many units it contains. That makes the approach simpler to explain and easier to use for ongoing preservation work.
This scheme, which combines building age and size, helps us describe the county’s naturally affordable housing stock intuitively: the smallest older multifamily buildings of 5 or more units (Core NOAH) tend to provide the largest rent discounts, mid-sized older buildings (Expanded NOAH) remain a large part of the naturally affordable stock, and somewhat larger pre-2000 buildings (Marginal NOAH) can still provide lower-cost housing even if they are not as affordable as the Core category.
The scale and location of NOAH in LA County
Based on the classification scheme described above, NOAH encompasses a large portion of Los Angeles County’s rental housing landscape. Countywide between 2020-2024, there were about 1.85 million occupied rental units, of which roughly 1.08 million (58%) were in multifamily buildings with 5 or more units.2 We estimate 460,000 Core NOAH units in pre-2000 buildings with 5-19 units (43% of multifamily units), 248,000 Expanded NOAH units in pre-2000 buildings with 20-49 units (23%), and 101,000 Marginal NOAH units in pre-2000 buildings with 50-99 units (9%), for a total of 809,000 units (see the chart below). Together, the three categories account for 75% of the county’s existing multifamily stock with 5 or more units, and more than half of these units fall into the most affordable category (Core NOAH).
Note: Numerators are from the 2024 Assessor data, number of units in the buildings with such characteristics. The “Other” category includes federally and state-subsidized housing units, and they account for a small share of the multifamily rental housing stock.
That scale is one of the most important findings in this chapter. Naturally affordable housing is not a small niche within the rental market; it is a major part of the county’s older apartment stock. Even though these older, smaller buildings offer rents that are lower than those in newer, larger properties, many of the households living in them are still paying a substantial share of their income toward housing and remain rent-burdened, as the renter affordability patterns documented later in this chapter make clear.
Supporting affordability in Los Angeles County will require not only expanding the subsidized housing stock, which will require substantial time and resources, but also preserving this much larger set of unsubsidized units. Future work is needed to track the scale and sources of NOAH loss over time, including redevelopment, rent increases, and deferred maintenance, to better target preservation efforts.
NOAH units are not evenly distributed across the county. To assess these units’ geographic distribution, we break the county into twelve submarkets that capture locally meaningful housing markets in Los Angeles County. To a much greater extent than jurisdictional boundaries do, these submarket areas correspond to distinct rent levels and housing conditions, as well as to the geographic patterns of where Angelenos search for units when they are in the rental housing market. These features make submarkets especially useful for telling the public story of where NOAH units are concentrated.
In raw numbers, from 2020-2024, the Hollywood-Studio City submarket contained the largest total NOAH stock, with about 155,000 units, followed by Long Beach-South Bay with 102,000, San Fernando Valley with 102,000, and Coastal Communities-Beverly Hills with 98,000. On the other end of the spectrum, Downtown had the smallest total, with 9,620 units (but also the second-lowest total in multifamily buildings with 5+ rental units), followed by Palmdale-Lancaster-Santa Clarita with about 13,000 and Pasadena with 14,000. Submarkets with more NOAH units tended to have lower median family incomes. See the chart below for counts of units by NOAH category across submarkets.
Note: Counts and numerators are from 2024 Assessor’s data, number of units in the buildings with such property characteristics; denominator is the IPUMS renter occupied units regardless of property characteristics.
Shifting from total NOAH counts to shares of submarkets’ total rental housing units reveals a slightly different geography of NOAH concentration. Koreatown-Mid City had the highest NOAH share, at 62% of existing rental units, followed by Hollywood-Studio City at 61% and Burbank-Glendale at 57%. Downtown and Palmdale-Lancaster-Santa Clarita are much lower, at 15% and 17%, respectively. These lower shares do not necessarily reflect an absence of older, lower-cost buildings; they also potentially indicate substantial post-2000 construction that expands the overall rental stock and, in doing so, reduces the share of units that meet the NOAH definition. See the map below for a map of each NOAH category across LA County submarkets.
There is more than one way to measure NOAH. One option is to use income-based measures, which define affordability based on households’ earnings and rent payments. Another is to use a simpler rule based on building characteristics, borrowed from earlier studies, such as focusing on older small multifamily buildings built before 1990 that are owned by mom-and-pop landlords, as opposed to institutional owners (Song & Reid, 2026).
These alternatives offer some advantages. Income-based measures connect affordability directly to household budgets, and property-based screens are often easier to apply than more detailed affordability calculations.
But each alternative also has important drawbacks in Los Angeles County. Income-based measures can be misleading because they rely on self-reported rents that may reflect below-market contract rents for long-term tenants rather than what a unit would rent for today. Moreover, they are highly sensitive to how local income thresholds are defined. They also rely on geographies that are too broad for parcel-level preservation planning.
The older small-building definition works reasonably well as a reference point, but it does not match Los Angeles County’s housing market as closely as our local definition does. In our data, the year 2000 is a more meaningful dividing line than 1990, and the distinction between 5-19, 20-49, and 50-99 unit buildings reveals important differences within the older stock (as seen in this chart). For this chapter, the main takeaway is simple: NDSC’s localized NOAH definition gives us a clearer picture of where naturally affordable housing actually sits in the market.
Who lives in NOAH units?
The following data visualizations shift the scale of analysis from units deemed as NOAH to households residing in NOAH units. These charts compare key characteristics of renters living in older NOAH multifamily properties (5+ units and built before 2000) with renters in single-family homes, buildings with 2-4 units, newer multifamily properties, and all renters across Los Angeles County. Due to data limitations, we cannot distinguish residents of multifamily rental buildings with 50-99 units and built before 2000 (Marginal NOAH) and rental buildings with 100+ units and built before 2000, which are part of the non-NOAH stock. We thus opt to report demographic characteristics of residents who live in rental buildings with 50+ units and built before 2000, referring to these units as “Marginal+ NOAH” in the following sections.3
When focusing only on households that are unlikely to be subsidized (i.e., those who could conceivably live in NOAH units; see Data & Methods page for more details), we see that NOAH serves renters who exhibit considerable diversity across race/ethnicity, household size and structure, educational attainment, and presence of older adults (age 62+).
The chart below shows that, from 2020-2024, Hispanic/Latino households made up a large share of renters across all NOAH categories, though they were underrepresented relative to the share of renter households headed by a Hispanic/Latino (42%). Hispanic/Latino-headed households accounted for 41% of likely-unsubsidized renter households that were living in Core NOAH units, 38% in Expanded NOAH units, and 32% in Marginal+ NOAH units. Asian-headed households, who accounted for about 13% of all LA County renters, were overrepresented in NOAH stock, particularly in larger buildings, while white- and Black-headed households appeared at shares close to or modestly above their countywide averages. The upshot is that NOAH supports a diverse renter population and benefits many different racial and ethnic groups across the county.
Note: This visualization is strictly examining data on renter households unlikely to be subsidized.
The chart below describes household size, the share of households with children, the education levels of household heads, and the share of households with older adults within units deemed to be NOAH. In all three NOAH types, household sizes tended to be smaller than in the overall rental market in Los Angeles County. The average household size among all LA County renters was 2.5, compared with 2.27 in Core NOAH units, 2.18 in Expanded NOAH units, and 1.95 in Marginal+ NOAH units. NOAH units in Los Angeles County were also less likely to house families with children. The share of households with children under age 18 among all LA County renter households was 29%; within NOAH, this share declines with building size, from 25% in Core NOAH units to 24% in Expanded NOAH units and 19% in Marginal+ NOAH units.
The share of households headed by an older adult moves in the opposite direction, rising with building size, especially in Marginal+ NOAH units. About a quarter of renter households living in Marginal+ NOAH buildings were headed by an adult aged 62 or above, which is substantially higher than the 18% share among renters living in all building types. These patterns suggest that smaller NOAH buildings may be disproportionately important for families: They house more children and larger households than the larger NOAH buildings, even though single-family homes and buildings with 2-4 units still house more children and larger families, on average. College degree attainment also rises modestly as NOAH building size increases, from 40% to 43%. Renter household heads in NOAH units were more likely to hold a college degree or above than those in buildings with 1-4 units (32%), but less likely than those in newer multifamily properties (51%). NOAH serves a broad range of households rather than a single tenant profile.
Note: This visualization is strictly examining data on renter households unlikely to be subsidized.
Next, the chart below highlights patterns of residential stability. Core NOAH units were more likely to have long-term tenants. In Core NOAH units, 31% of households have lived there for 10 years or more, compared with 28% in Expanded NOAH units and 22% in Marginal+ NOAH units. This pattern shows that NOAH units are not only notable for their lower rent levels; older multifamily properties, particularly smaller ones, also support longer-term residence and neighborhood stability. At the same time, higher-income residents may be somewhat less likely to move out of these units, which can limit turnover. However, on the whole, when these units disappear or become unaffordable, the impact is likely to fall disproportionately on many long-tenured households, as opposed to recent movers.
Note: This visualization is strictly examining data on renter households unlikely to be subsidized.
The chart below sharpens the affordability story. Median household income was $65,704 in Core NOAH units, $62,400 in Expanded NOAH units, and $54,980 in Marginal+ NOAH units. These figures were below the median income of renters in post-2000 multifamily properties ($74,938) and well below the median for renters in single-family units ($85,747). The 25th percentile income in Marginal+ NOAH buildings falls well below the corresponding quartile in smaller NOAH properties. This suggests that these larger, older properties have a high concentration of the county’s lowest-income, unsubsidized renters. At the same time, median gross rent was lower in the NOAH stock than in newer multifamily buildings: about $1,910 in the Core NOAH category, $1,912 in the Expanded NOAH category, and $2,004 in the Marginal+ NOAH category, compared with $2,479 in post-2000 multifamily properties. This gradient in rent levels reinforces the validity of our NOAH definition.
Note: This visualization is strictly examining data on renter households unlikely to be subsidized.
Even with these lower rents, many households in NOAH still earned substantially less than renters in newer multifamily properties or single-family homes and therefore remained strained by housing costs. A useful way to see this is to hold renter income constant at the county median and estimate the rent that such a household would pay in each building type. On that basis, NOAH units were still more affordable than newer 5+ unit properties and single-family units, and differences across NOAH size categories were relatively modest. Together, these patterns suggest that NOAH offers meaningfully lower rents for the broader renter population, but the households who currently occupy this stock often have lower incomes than the typical renter and therefore still face tight budgets even in these lower-cost buildings.
Conclusion
In sum, Los Angeles County’s rental market depends heavily on older multifamily buildings that are unsubsidized, widely available, and cheaper than newer alternatives, even though many tenants in those buildings still face severely tight budgets. That renders NOAH central to both the county’s affordability challenge and any realistic strategy for responding to it. Subsidized (i.e., non-NOAH) affordable housing units also play an important role but cannot be scaled up quickly enough to fully substitute for the NOAH stock.
We conclude this feature chapter by reinforcing three simple points. First, NOAH is large in scale, with approximately 809,000 units identified countywide in NDSC’s three-tier framework. Core NOAH units account for about a quarter of the total occupied rental units in LA County. Second, the households living in this stock are diverse, often long-tenured, and frequently rent-burdened, though to a lesser extent than renter households in newer stock. Third, these NOAH units are distributed unevenly across submarkets, so preservation risks and opportunities vary across the county. Taken together, these findings suggest protecting NOAH helps ensure some level of affordability and stability in LA County’s very challenging rental housing market. But preservation alone is not sufficient: Even in Core NOAH buildings, the most affordable tier, typical renters remained cost-burdened, underscoring that expanding subsidized housing and boosting renter incomes remain essential complements to any NOAH preservation strategy.
Contributors
- Authors
- Jorge De la Roca, USC Lusk Center for Real Estate
- Jared N. Schachner, USC Price School of Public Policy
- Jiaqi Dong, USC Lusk Center for Real Estate
- Research Team
- Christa Tang, USC Lusk Center for Real Estate
- Cameron Yap, USC Lusk Center for Real Estate
- Elizabeth Grubb, USC Lusk Center for Real Estate
- Adela G Ortiz, USC Lusk Center for Real Estate
- Christine Steinmann, USC Lusk Center for Real Estate
Citations
Barker, D. (2003). Length of residence discounts, turnover, and demand elasticity. Should long-term tenants pay less than new tenants? Journal of Housing Economics, 12(1), 1–11. https://doi.org/10.1016/S1051-1377(03)00002-0
Guasch, J. L., & Marshall, R. C. (1987). A theoretical and empirical analysis of the length of residency discount in the rental housing market. Journal of Urban Economics, 22(3), 291–311. https://doi.org/10.1016/0094-1190(87)90029-5
NYU Furman Center. (2024). The use of Housing Choice Vouchers in New York City. Link
Song, T., & Reid, C. (2026). The Implications of Naturally Occurring Affordable Housing (NOAH) Sales for Residential Mobility. Journal of the American Planning Association, 92(3), 360–374. https://doi.org/10.1080/01944363.2026.2618647
Footnotes
- We attempted to exclude all subsidized housing from NOAH estimates for the analysis in this chapter, but we were only able to remove federally and state-subsidized properties from our estimates due to difficulties acquiring reliable and comprehensive data on local subsidy programs across the entire county. Our NOAH counts are thus likely to be overestimated, though in future work we will refine them as we gain a more complete understanding of local subsidy programs in the county.
- Based on IPUMS 2020-2024 5-year data. Throughout the chapter, we focus on occupied renter households and do not account for vacant rental units. We use 5-year rather than 1-year data because the chapter examines detailed demographic characteristics, and the larger sample provides more statistically reliable estimates.
- The Census provides more detailed categories for smaller buildings, but groups all buildings with 50 or more units into a single category, preventing us from distinguishing between buildings with 50-99 units and those with 100 or more units.
