The majority of lease payments we receive from our residents and tenants are fixed. We receive variable payments from our residents and commercial tenants primarily for utility reimbursements. Our total lease income, included in continuing operations, was comprised of the following amounts for all operating leases for the year ended December 31, 2020 (in thousands):

	2020			2019
Fixed lease income	$	677,060		$	722,146
Variable lease income		43,588			46,494
Straight-line rent write-off (1)		(2,850	)		—
Total lease income	$	717,798		$	768,640

(1) We monitor the collectability of all unpaid rent amounts. The onset of COVID-19 and the anticipated economic slowdown resulted in a $2.9 million write-off of accrued straight-line rent during the year ended December 31, 2020.

In response to the economic effects of the COVID-19 pandemic and governmental lockdowns, many jurisdictions where our communities are located have enacted protections for residents and commercial tenants, including government-mandated rent deferrals, rent freezes, repayment extensions, fee abatement measures or concessions, and prohibitions on lease terminations or evictions for tenants. Some states and municipalities are also implementing rental assistance programs and encouraging landlord-tenant negotiations.

On April 10, 2020, the FASB issued a Staff Q&A to respond to some frequently asked questions about accounting for lease concessions, including deferrals or reductions of future lease payments. Consequently, in accordance with the Staff Q&A issued by the FASB, we may elect to record rent relief when granted rather than over the remaining term of the lease.

In general, our commercial leases have options to extend for a certain period of time at the tenant’s option. Future minimum annual rental payments we are contractually obligated to receive under commercial leases, excluding such extension options, are as follows as of December 31, 2020 (in thousands):

2021	$	13,184
2022		13,488
2023		12,584
2024		11,170
2025		9,513
Thereafter		47,476
Total	$	107,415

Generally, our residential leases do not provide extension options and, as of December 31, 2020, have an average remaining term of 8.5 months.

Commencing on January 1, 2021, we had leased four redevelopment properties to Aimco, resulting in $25.3 million of expected 2021 lease payments. The lease payments related to the four redevelopment properties have not been included in the table above.

Beginning in 2019, we recognize right of use assets and related lease liabilities, which are included in other assets and accrued liabilities and other, respectively, in our consolidated balance sheets. We estimated the value of the lease liabilities using a discount rate equivalent to the rate we would pay on a secured borrowing with similar terms to the lease. On October 1, 2019, we revised our estimate of the incremental borrowing rate, which resulted in a reduction of our right of use assets and related lease liabilities for ground leases. The adjustment recorded to our right of use assets and lease liabilities did not impact our consolidated statements of operations.

Substantially all of the payments under our ground and office leases are fixed. We exclude options to extend the lease in our minimum lease terms unless the option is reasonably certain to be exercised. Our total lease cost for ground and office leases for the years ended December 31, 2020, 2019, and 2018 was $8.0 million, $10.7 million, and $5.1 million, respectively.

As of December 31, 2020, the ground and office leases have weighted-average remaining terms of 73.3 years and 7.6 years, respectively, and weighted-average discount rates of 6.6% and 3.6%, respectively. Minimum annual rental payments under these operating leases, reconciled to the lease liability included in accrued liabilities and other in our consolidated balance sheets, are as follows (in thousands):

	Operating Lease Future Minimum Rent
2021	$	4,548
2022		4,280
2023		3,727
2024		3,749
2025		3,770
Thereafter		421,228
Total	$	441,302
Less: Discount		(385,933	)
Total lease liability	$	55,369