In addition to presenting FFO in accordance with the NAREIT definition, we also disclose normalized FFO,which adjusts FFO for items that relate to unanticipated or non-core events or activities or accounting changes that, if not noted, would make comparison to prior period results and market expectations less meaningful to investors and analysts. We believe that the use of FFO, combined with the required GAAP presentations, improves the understanding of our operating results among investors and the use of normalized FFO makes comparisons of our operating results with prior periods and other companies more meaningful. While FFO and normalized FFO are relevant and widely used supplemental measures of operating and financial performance of REITs, they should not be viewed as a substitute measure of our operating performance since the measures do not reflect either depreciation and amortization costs or the level of capital expenditures and leasing costs necessary to maintain the operating performance of our properties, which can be significant economic costs that could materially impact our results of operations. FFO and normalized FFO should not be considered an alternative to net income (loss) (computed in accordance with GAAP) as indicators of our financial performance or to cash flow from operating activities (computed in accordance with GAAP) as an indicator of our liquidity.
We calculate adjusted funds from operations, or AFFO, by subtracting from or adding to normalized FFO (i) unbilled rent revenue, (ii) non-cash share-based compensation expense, and (iii) amortization of deferred financing costs. AFFO is an operating measurement that we use to analyze our results of operations based on the receipt, rather than the accrual, of our rental revenue and on certain other adjustments. We believe that this is an important measurement because our leases generally have significant contractual escalations of base rents and therefore result in recognition of rental income that is not collected until future periods, and costs that are deferred or are non-cash charges. Our calculation of AFFO may not be comparable to AFFO or similarly titled measures reported by other REITs. AFFO should not be considered as an alternative to net income (calculated pursuant to GAAP) as an indicator of our results of operations or to cash flow from operating activities (calculated pursuant to GAAP) as an indicator of our liquidity.