July 1, 2021

Contact: Mark Church, Assessor-County Clerk-Recorder & Chief Elections Officer
Alternate: Jim Irizarry, Assistant Assessor-County Clerk-Recorder
Alternate: Terry Flinn, Special Assistant to the Assessor

(Redwood City, CA) San Mateo County Assessor-County Clerk-Recorder Mark Church today announced the county’s Property Assessment Roll increased year-over-year by $10.6 billion, or 4.16%, to a record high of over $265.8 billion in assessed value.

“2020 marked another year of roll growth for San Mateo County,” said Church. “This year’s increase was largely due to record-setting single-family home values driven by strong demand for homes during the pandemic. Increased residential values were the surprise of 2020 given that the county was under Shelter-In-Place mandates for much of the year due to the ongoing COVID-19 pandemic.”

The story was mixed with commercial properties, with some declining values but growth overall. The Assessor’s Office reached out to nearly 700 owners of recently re-assessed commercial property, with 120 of those qualifying for a temporary decline in assessed value. “San Mateo County is also home to many life sciences companies that grew during the pandemic,” noted Church. “This sector generated a significant portion of the commercial leasing activity and planned construction in 2020, and we forecast that will continue in coming years.”

The combined assessment roll has increased by $124.9 billion from eleven years ago. This is the eleventh consecutive year in which a new historical high has been set. The secured portion of the roll, which is approximately 96.2% of the total roll and primarily consists of real property, increased in value by 4.79%. The unsecured portion makes up the remaining 3.8% of the total roll, and declined in value by 9.67%. The unsecured roll includes business assets including commercial airline property at San Francisco International Airport (SFO) and business property in leased locations throughout the County.

The effect of Shelter-In-Place on businesses is directly related to the reduction of the unsecured roll value. The San Jose Mercury News reported in September that out of the “roughly 8,300 businesses that have closed in the Bay Area since the start of the pandemic, about 3,800 of them permanently.”

On the other hand, the growth rate for single-family homes in San Mateo County saw an increase in the median sales price of 8.97%, to $1,700,000. This made 2020 another year of strong growth for residential properties, despite a slight decline of 1.07% in the condominium and townhome segment of the market. The reason for weak demand in this segment was pointed out by the San Jose Spotlight in October of last year, which quoted Jordan Levine, Deputy Chief Economist for the California Association of Realtors, that “the economic effects of the shutdown have been more concentrated in lower- and middle-income households. This is where most of the condo demand comes from given the affordability constraints most families face in California.”

However, with the pandemic on the retreat, the economy should be quickly returning to normal now. According to the State of California Employment Development Department, unemployment in San Mateo County, home to strong technology and life science industries, has decreased to 5.8%, as of December 2020, the second lowest rate in California.

“San Mateo County consists of a diverse economic base, from the airline transportation industry at SFO to many 21st century technology giants including Facebook, Google, Gilead and Genentech,” stated Church. “For years, a large percentage of our assessment roll was concentrated in the airline industry at SFO, and the adverse impacts of COVID-19 on the assessment roll would have been much greater. However, today our diverse economic base and the growing economic strength of our technology and bioscience industries contribute to a more favorable long-term outlook.”

Highlights of the 2021 Roll

The 2021-22 Property Assessment Roll reflects overall growth throughout the County. Total assessed values increased in all 20 cities and unincorporated areas, with increases ranging from 1.73% to as high as 7.43%, and an overall increase of 4.16%. The County’s unincorporated areas, which include San Francisco International Airport (SFO), experienced a negative growth rate of -0.85%; primarily due to reductions in commercial aircraft assessments.

The top 5 cities with the highest percentage growth in Assessed Value are:​

  • San Carlos (+7.43%)
  • Menlo Park (+7.29%)
  • Brisbane (+6.63%)
  • South San Francisco (+6.28%)
  • Atherton (+5.68%)

The top 5 cities with the highest dollar growth in Assessed Value are:​

  • Menlo Park - $1.65 Billion
  • South San Francisco - $1.45 Billion
  • San Mateo - $1.08 Billion
  • San Carlos - $0.95 Billion
  • Redwood City - $0.79 Billion

The assessed value increases in these 5 cities total over 56% of the roll increase for the 2021-2022 Roll.
The shared property tax funding base is approximately 1% of the county’s Property Assessment Roll and will thus increase to $2.66 billion. Approximately 45% of revenue is allocated to schools within the county, 25% to the County, 18% to cities, 10% to special districts, and 2% to former redevelopment agencies. “The county’s share will be 25%, or approximately $665 million, an increase of $27 million over last year,” noted Church.

The Property Assessment Roll is the assessed value of all properties as of January 1 each year, and reflects changes in ownership, new construction, value declines, and value restorations from the previous January 1. The Property Assessment Roll is composed of two sections, the Secured Roll and the Unsecured Roll. When combined, the two sections are referred to as the Combined Roll.


The Secured Roll represents over 96% of the Combined Roll and includes 222,140 commercial, residential and agricultural real properties.This year, the Secured Roll increased to $256 billion, an increase of $11.69 billion or 4.79% over 2020-21, reflecting continued economic growth in the county.

The growth of the San Mateo County Secured Roll is primarily due to the following factors:

New Commercial Development. Commercial and mixed-use construction were major contributors to the 2021-22 Roll growth. Major projects in the county, consisting of 80,000 square feet or more, accounted for more than 2 million square feet of new development coming to market in 2020. In all, 52 million square feet of new construction are expected to be completed in the county over the next six to eight years. A total of 15.8 million square feet are under construction, 10.9 million square feet have planning approval, and 25 million square feet are under review. Approximately 13.1 million square feet of new construction have been completed in the last five years.

Commercial projects account for 63% of all major construction projects being tracked by the Assessor’s office. The following table shows the percentages attributed to each of the major use-types in the county’s development pipeline.

New Major Development​


Office 26%
Life Science 19%
Master Planned Community 11%
Hotel 3%
Senior Care Facility 2%
Retail 2%
Hospital 1%
Commercial Sq. Ft. 63%
Residential Sq. Ft. 37%
Grand Total 100%

Top 5 Cities for New Commercial Development. The following cities have the greatest amount of major development, consisting of projects that are 80,000 square feet or more, that are pending, approved, or under construction:

  • Redwood City – 15.6 million square feet
  • Menlo Park – 11.4 million square feet
  • South San Francisco – 9.2 million square feet
  • Brisbane – 8.2 million square feet
  • San Mateo – 4.8 million square feet

“Growth in the technology and life science sectors continues to drive the demand in office, housing, lodging and retail,” said Church.

Completed commercial projects in 2020 include the Stanford office complex in Redwood City. Life Sciences was led by the completion of the Centennial Tower in South San Francisco and the Bay Meadows office project in San Mateo, with a combined total of over 1.5 million square feet of commercial development completed in those projects.

Residential completions were led by the Wheeler Plaza project in San Carlos. Other apartment complex projects completed include those at 4619 Brunswick Street and 2001 Ocean View Avenue, both in Daly City, with a combined total of over 0.5 million square feet of residential development completed in those projects.

Sales and Ownership Changes. Sales and changes in ownership totaled $7.5 billion, or about 64% of this year’s Secured Roll increase. Residential sales accounted for about 69% of that dollar growth while commercial sales accounted for 31%.

According to the San Mateo County Association of Realtors (SAMCAR), the median sales price of single-family homes in San Mateo County increased by 8.97% in 2020 to $1,700,000, as compared to the median price of $1,560,000 in 2019. Total dollar value of sales increased by 12.1% and the number of sales increased by 2.14% for the calendar year. Residential values are still near record high, so when residential property is re-assessed at market value due to a change in ownership, the new value can be substantially higher than the previous assessment. These price-level changes account for the substantial impact residential reassessments have on roll growth overall.

Restoration of Assessed Value: Proposition 8/Decline in Value Program. The Proposition 8/Decline in Value Program provides property tax relief to property owners when the market value of a property falls below its assessed value. The number of residential properties qualifying for the Proposition 8/Decline in Value Program increased slightly to 392 in 2020-21, from 295 in 2019-20, but still remains significantly below the record high of 34,700 properties in FY 2011-12. On the commercial side, a pro-active review program initiated by the Assessor’s Office to identify COVID-19 affected properties, found an additional 132 commercial properties that qualified for property tax relief, which is in addition to the 54 properties already in the program, a number still substantially below the high of 604 properties in FY 2012-13.

Over the next few days, more than 392 residential property owners enrolled in the program will be mailed their 2021-22 Assessed Value Notices, with 48 being fully restored to their factored base-year (Proposition 13) values.

Annual Inflation Factor. Proposition 13, which governs property taxation in California, ties the annual inflation factor to the California Consumer Price Index (CCPI) issued by the California Industrial Relations Board and limits annual inflation increases of assessed value to no more than 2%. This year an annual inflation factor of 1.01036% was applied to the 2021-22 assessed value of all real property that did not have a change in ownership or any new construction during 2020.

Foreclosures. There were 12 Trustee’s Deeds recorded in calendar year 2020, a 70% decrease from the 40 recorded in 2019. Notice of Defaults decreased 53.7% from 376 in 2019 to 174 in 2020, continuing the downward trend in defaults since the high of 5,058 in 2009.

“Foreclosure activities continued to decline, another important indicator of the strength of the local economy,” said Church.


The Unsecured Roll comprises approximately 4% of the Property Assessment Roll and includes the valuations of business/personal property, air transportation related property at SFO and possessory interests (leased government property). This year, the Unsecured Roll decreased to $10.0 billion in assessed value, a decrease of almost $1.0 billion or 9.67% over the prior year’s Unsecured Roll. This decrease was primarily related to reductions in commercial airlines property values at SFO. Most of the Unsecured Roll is business or personal property, which typically depreciates and is not subject to an annual inflationary value increase, as is real property on the Secured Roll.


2021-22 Local Combined Roll
2021-22 Local Secured Roll
2021-22 Local Unsecured Roll
2021-22 Residential Decline in Value Summary
Graph of Historical Combined Property Assessment Roll Values, 2010 through 2021

Related Contacts

Mark Church

Assessor-County Clerk-Recorder and Chief Elections Officer
555 County Center
Redwood City, CA 94063-1665Get Directions

Jim Irizarry

Asst. Assessor-County Clerk-Recorder & Asst. Chief Elections Officer
555 County Center
Redwood City, CA 94063-1665Get Directions

Terry Flinn

Special Assistant to the Assessor