All of the Company’s leases are classified as operating leases. The Company's Lease income is comprised of both fixed and variable income, as follows:

Fixed and in-substance fixed lease income includes stated amounts per the lease contract, which are primarily related to base rent, and in some cases stated amounts for common area maintenance (“CAM”), real estate taxes, and insurance. Income for these amounts is recognized on a straight- line basis.

Variable lease income includes the following two main items in the lease contracts:

(i) Recoveries from tenants represents amounts tenants are contractually obligated to reimburse the Company for the tenants’ portion of actual Recoverable Costs incurred. Generally the Company’s leases provide for the tenants to reimburse the Company based on the tenants’ share of the actual costs incurred in proportion to the tenants’ share of leased space in the property.

(ii) Percentage rent represents amounts billable to tenants based on the tenants' actual sales volume in excess of levels specified in the lease contract.

The following table provides a disaggregation of lease income recognized under ASC Topic 842 as either fixed or variable lease income based on the criteria specified in ASC 842:

(in thousands)	Three months ended March 31,
	2020			2019
Operating lease income
Fixed and in-substance fixed lease income	$	204,943			202,163
Variable lease income		64,668			62,835
Other lease related income, net:
Above/below market rent and tenant rent inducement amortization		12,880			13,454
Uncollectible straight line rent		(3,902	)		(285	)
Uncollectible amounts in lease income		(4,052	)		(864	)
Total lease income	$	274,537			277,303

Lease income for operating leases with fixed payment terms is recognized on a straight-line basis over the expected term of the lease for all leases for which collectibility is considered probable at the commencement date. At lease commencement, the Company generally expects that collectibility is probable due to the Company’s credit checks on tenants and other creditworthiness analysis undertaken before entering into a new lease; therefore, income from most operating leases is initially recognized on a straight-line basis. For operating leases in which collectibility of Lease income is not considered probable, Lease income is recognized on a cash basis and all previously recognized straight-line rent receivables are reversed in the period in which the Lease income is determined not to be probable of collection. In addition to the lease-specific collectability assessment performed under Topic 842, the Company also recognizes a general reserve, as a reduction to Lease income, for its portfolio of operating lease receivables which are not expected to be fully collectible based on the Company’s historical collection experience.

During the three months ended March 31, 2020, the Company experienced a higher rate of uncollectible lease income driven by changes in expectations of collectibility for certain tenants given the expected impact of the COVID-19 pandemic to our tenants.

Additionally, certain tenants experiencing economic difficulties during this pandemic may seek future rent relief, which may be provided in the form of rent abatement or rent deferrals, among other possible agreements. Under Topic 842, subsequent changes to lease payments that are not stipulated in the original lease contract are generally accounted for as lease modifications. Due to the number of lease contracts that would require analysis to determine, on a lease by lease basis, whether such a concession is required to be accounted for as a lease modification, the FASB staff provided clarity as to an acceptable approach in accounting for lease concessions related to the effects of the COVID-19 pandemic. The FASB staff provided guidance that it would be acceptable for entities to make an election to account for lease concessions related to the effects of the COVID-19 pandemic consistent with how those concessions would be accounted for under Topic 842 as though enforceable rights and obligations for those concessions existed in the existing lease contract, thereby not requiring entities to apply lease modification guidance to those contracts. The Company is evaluating the options to account for such COVID-19 concessions.