the allowance calculation is also supplemented with qualitative reserves that takes into consideration the current portfolio and specific risk characteristics , such as changes in underwriting standards , portfolio mix , delinquency level , or term , as well as changes in environmental conditions , among other factors , that have occurred but are not yet reflected in the quantitative model component . although management believes that it uses the best information available to establish the allowance for credit losses , future adjustments to the allowance for credit losses may be necessary and results of operations could be adversely affected if circumstances differ substantially from the assumptions used in making the determinations . because future events affecting borrowers and collateral can not be predicted with certainty , there can be no assurance that the existing allowance for credit losses is adequate or that increases will not be necessary should the quality of loans deteriorate as a result of the factors discussed previously . any material increase in the 31 allowance for credit losses may adversely affect our financial condition and results of operations . the allowance is based on information known at the time of the review . changes in factors underlying the assessment could have a material impact on the amount of the allowance that is necessary and the amount of provision to be charged against earnings . such changes could impact future results . for further information related to our allowance for credit losses , see note 1 ( f ) of the notes to the consolidated financial statements . valuation of investment securities . our investment securities are classified as either held-to-maturity or available-for-sale . held-to-maturity securities are carried at amortized cost , while available-for-sale securities are carried at fair value . unrealized gains or losses on available-for-sale securities , net of deferred taxes , are reported in other comprehensive income . fair values are determined as described in note 17 of the notes to the consolidated financial statements . semi-annually ( at may 31 and november 30 ) , we validate the prices received from third parties by comparing them to prices provided by a different independent pricing service . we have reviewed the detailed valuation methodologies provided to us by our pricing services . additional information related to our investment securities can be found in note 1 ( d ) of the notes to the consolidated financial statements . on a quarterly basis , we measure expected credit losses on held-to-maturity debt securities on a collective basis by major security type . available-for-sale debt securities in an unrealized loss position are reviewed for impairment at least quarterly . an investment security is deemed impaired if the fair value of the investment is less than its amortized cost . in making this determination , we consider both our intent to sell and the likelihood that we will not have to sell the investment securities before recovery of their amortized cost basis during our evaluation . for available-for-sale debt securities that do not meet this criteria , we evaluate whether the decline in fair value has resulted from credit losses or other factors . in making this assessment we consider the issuer of the securities and their creditworthiness , any changes to the rating of the security and any adverse conditions specifically related to the security , among other factors . also , we may evaluate the business and financial outlook of the issuer , as well as broader economic performance indicators . if this assessment indicates that a credit loss exists , the present value of cash flows expected to be collected from the security is compared to the amortized cost basis of the security . if the present value of cash flows expected to be collected is less than the amortized cost basis , a credit loss exists and an allowance for credit losses is recorded for the credit loss , limited by the amount that the fair value is less than amortized cost . any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income . any future deterioration in the fair value of an investment security , or the determination that impairment exists , may have a material adverse affect on future earnings . goodwill . goodwill is not subject to regular amortization but instead is required to be tested for impairment at least annually and possibly more frequently if certain events occur or changes in circumstances arise . in testing goodwill for impairment , we have the option to first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value . if , after assessing the totality of events and circumstances , we determine it is not more likely than not that the fair value of a reporting unit is less than its carrying value , then performing the impairment test would be unnecessary . however , if we conclude otherwise , it would then be required to perform the quantitative impairment test . in the quantitative impairment test , the fair value of each reporting unit is compared to its carrying amount in order to determine if impairment is indicated . if the estimated fair value exceeds the carrying amount , the reporting unit is not deemed to be impaired . if the estimated fair value is below the carrying value of the reporting unit , the difference is the amount of impairment . determining the fair value of a reporting unit requires a high degree of subjective judgment , including developing cash flow projections , selecting appropriate discount rates , identifying relevant market comparables , incorporating general economic and market conditions and selecting an appropriate control premium . story_separator_special_tag interest income on loans receivable increased by $ 16.1 million , or 4.1 % , to $ 410.9 million for the year ended december 31 , 2020 from $ 394.8 million for the year ended december 31 , 2019. this increase in interest income on loans receivable is attributed to increases in the average balance on loans receivable . the average balance increased by $ 1.549 billion , or 18.1 % , to $ 10.104 billion for the year ended december 31 , 2020 from $ 8.555 billion for the year ended december 31 , 2019. this increase is due primarily to the addition of $ 1.517 billion , at fair value , of loans related to the mutualbank acquisition and organic loan growth of $ 255.2 million . contributing to this organic loan growth was the origination of approximately $ 500.0 million of ppp loans . included in loan interest income for the year ended december 31 , 2020 is $ 3.1 million of accretion related to mutualbank loan purchase accounting and $ 5.7 million of accretion related to ppp fees , net of origination costs . partially offsetting this increase in average balances was a decrease in the average yield on loans receivable to 4.07 % for the year ended december 31 , 2020 from 4.61 % for the year ended december 31 , 2019 primarily due to the decrease in market interest rates . interest income on mortgage-backed securities increased by $ 746,000 , or 4.5 % , to $ 17.4 million for the year ended december 31 , 2020 from $ 16.7 million for the year ended december 31 , 2019. this increase is the result of an increase in the average balance of mortgage-backed securities by $ 250.0 million , or 39.1 % , to $ 889.7 million for the year ended december 31 , 2020 from $ 639.8 million for the year ended december 31 , 2019. this increase was primarily a result of investment securities received as part of the mutualbank acquisition as well as additional purchases utilizing excess cash from deposit growth during the current year . partially offsetting this increase was a decrease in the average yield on mortgage-backed securities to 1.96 % for the year ended december 31 , 2020 from 2.61 % for the year ended december 31 , 2019. this decrease in yield was partially due to the assumption of mortgage-backed securities from mutualbank with market yields lower than the existing northwest portfolio due to mark-to-market purchase accounting adjustments . in addition , new security purchases were made at lower yields due to decreases in market interest rates . interest income on investment securities remained relatively flat , decreasing by $ 200,000 , or 4.7 % , to $ 4.0 million for the year ended december 31 , 2020 from $ 4.2 million for the year ended december 31 , 2019. this decrease is the result of a decrease in the average balance of investment securities of $ 9.7 million , or 4.7 % , to $ 196.1 million for the year ended december 31 , 2020 from $ 205.8 million for the year ended december 31 , 2019 , which was primarily due to the maturity or call of government agency securities . the average yield on investment securities remained flat at 2.06 % for the years ended december 31 , 2020 and december 31 , 2019. dividends on fhlb stock decreased by $ 75,000 , or 7.1 % , to $ 1.0 million for the year ended december 31 , 2020 from $ 1.1 million for the year ended december 31 , 2019. this decrease is the result of decreases in the average yield on fhlb stock which decreased to 4.50 % for the year ended december 31 , 2020 from 7.29 % for the year ended december 31 , 2019. the fhlb of pittsburgh recently decreased yields on required stock holdings in reaction to lower market interest rates . slightly offsetting this decrease was an increase in the average balance on fhlb stock by $ 7.3 million , or 50.5 % , to $ 21.8 million for the year ended december 31 , 2020 from $ 14.5 million for the year ended december 31 , 2019 primarily due to fhlb stock acquired and retained from mutualbank . required fhlb stock holdings fluctuate with , among other things , the utilization of our borrowing capacity as well as capital requirements established by the fhlb . interest income on interest-earning deposits increased by $ 119,000 , or 19.8 % , to $ 719,000 for the year ended december 31 , 2020 from $ 600,000 for the year ended december 31 , 2019. this increase is attributable to an increase in the average balance of interest-earning deposits . the average balance increased by $ 497.4 million to $ 520.7 million for the year ended december 31 , 2020 from $ 23.3 million for the year ended december 31 , 2019 due to excess liquidity from recent deposit inflows . partially offsetting this increase was a decrease in the average yield on interesting-earning deposits to 0.14 % for the year ended december 31 , 2020 from 2.54 % for the year ended december 31 , 2019 , as a result of the federal reserve decreasing their targeted federal funds rate . interest expense . interest expense decreased by $ 14.6 million , or 25.6 % , to $ 42.3 million for the year ended december 31 , 2020 from $ 56.9 million for the year ended december 31 , 2019. this decrease in interest expense was primarily due to the decline in the average cost of interest-bearing liabilities which decreased to 0.49 % for the year ended december 31 , 2020 from 0.82 % for the year ended december 31 , 2019. this decrease resulted from decreases in the interest rates paid on deposits and borrowed funds in response to decreases in market interest rates . partially offsetting this

liquidity and capital resources northwest bank is required to maintain a sufficient level of liquid assets , as determined by management and defined and reviewed for adequacy by the fdic during their regular examinations . the fdic , however , does not prescribe by regulation a minimum amount or percentage of liquid assets . the fdic allows us to consider any unencumbered , available-for-sale marketable security , whose sale would not impair our capital adequacy , to be eligible for liquidity . liquidity is monitored through the use of a standard liquidity ratio of liquid assets to borrowings plus deposits . using this formula , northwest bank 's liquidity ratio was 16.78 % as of december 31 , 2020. we adjust our liquidity level in order to meet funding needs of deposit outflows , repayment of borrowings and loan commitments . we also adjust liquidity as appropriate to meet our asset and liability management objectives . liquidity needs can also be met by temporarily drawing upon lines-of-credit established for such reasons . at december 31 , 2020 , northwest bank had $ 3.872 billion of additional borrowing capacity available with the fhlb of pittsburgh , including a $ 250.0 million overnight line of credit , which had no balance at december 31 , 2020 , as well as $ 95.4 million of borrowing capacity available with the federal reserve bank and $ 110.0 million with three correspondent banks . in addition to deposits , our primary sources of funds are the amortization and repayment of loans and mortgage-backed securities , maturities of investment securities and other short-term investments , and earnings and funds provided from operations . while scheduled principal repayments on loans and mortgage-backed securities are a relatively predictable source of funds , deposit flows and loan prepayments are greatly influenced by general interest rate levels , economic conditions , and competition . we manage the pricing of our deposits to maintain a desired deposit balance . in addition , we invest excess funds in short-term interest earning and other assets , which provide liquidity to meet lending requirements .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```liquidity and capital resources northwest bank is required to maintain a sufficient level of liquid assets , as determined by management and defined and reviewed for adequacy by the fdic during their regular examinations . the fdic , however , does not prescribe by regulation a minimum amount or percentage of liquid assets . the fdic allows us to consider any unencumbered , available-for-sale marketable security , whose sale would not impair our capital adequacy , to be eligible for liquidity . liquidity is monitored through the use of a standard liquidity ratio of liquid assets to borrowings plus deposits . using this formula , northwest bank 's liquidity ratio was 16.78 % as of december 31 , 2020. we adjust our liquidity level in order to meet funding needs of deposit outflows , repayment of borrowings and loan commitments . we also adjust liquidity as appropriate to meet our asset and liability management objectives . liquidity needs can also be met by temporarily drawing upon lines-of-credit established for such reasons . at december 31 , 2020 , northwest bank had $ 3.872 billion of additional borrowing capacity available with the fhlb of pittsburgh , including a $ 250.0 million overnight line of credit , which had no balance at december 31 , 2020 , as well as $ 95.4 million of borrowing capacity available with the federal reserve bank and $ 110.0 million with three correspondent banks . in addition to deposits , our primary sources of funds are the amortization and repayment of loans and mortgage-backed securities , maturities of investment securities and other short-term investments , and earnings and funds provided from operations . while scheduled principal repayments on loans and mortgage-backed securities are a relatively predictable source of funds , deposit flows and loan prepayments are greatly influenced by general interest rate levels , economic conditions , and competition . we manage the pricing of our deposits to maintain a desired deposit balance . in addition , we invest excess funds in short-term interest earning and other assets , which provide liquidity to meet lending requirements .
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 Suspicious Activity Report : the allowance calculation is also supplemented with qualitative reserves that takes into consideration the current portfolio and specific risk characteristics , such as changes in underwriting standards , portfolio mix , delinquency level , or term , as well as changes in environmental conditions , among other factors , that have occurred but are not yet reflected in the quantitative model component . although management believes that it uses the best information available to establish the allowance for credit losses , future adjustments to the allowance for credit losses may be necessary and results of operations could be adversely affected if circumstances differ substantially from the assumptions used in making the determinations . because future events affecting borrowers and collateral can not be predicted with certainty , there can be no assurance that the existing allowance for credit losses is adequate or that increases will not be necessary should the quality of loans deteriorate as a result of the factors discussed previously . any material increase in the 31 allowance for credit losses may adversely affect our financial condition and results of operations . the allowance is based on information known at the time of the review . changes in factors underlying the assessment could have a material impact on the amount of the allowance that is necessary and the amount of provision to be charged against earnings . such changes could impact future results . for further information related to our allowance for credit losses , see note 1 ( f ) of the notes to the consolidated financial statements . valuation of investment securities . our investment securities are classified as either held-to-maturity or available-for-sale . held-to-maturity securities are carried at amortized cost , while available-for-sale securities are carried at fair value . unrealized gains or losses on available-for-sale securities , net of deferred taxes , are reported in other comprehensive income . fair values are determined as described in note 17 of the notes to the consolidated financial statements . semi-annually ( at may 31 and november 30 ) , we validate the prices received from third parties by comparing them to prices provided by a different independent pricing service . we have reviewed the detailed valuation methodologies provided to us by our pricing services . additional information related to our investment securities can be found in note 1 ( d ) of the notes to the consolidated financial statements . on a quarterly basis , we measure expected credit losses on held-to-maturity debt securities on a collective basis by major security type . available-for-sale debt securities in an unrealized loss position are reviewed for impairment at least quarterly . an investment security is deemed impaired if the fair value of the investment is less than its amortized cost . in making this determination , we consider both our intent to sell and the likelihood that we will not have to sell the investment securities before recovery of their amortized cost basis during our evaluation . for available-for-sale debt securities that do not meet this criteria , we evaluate whether the decline in fair value has resulted from credit losses or other factors . in making this assessment we consider the issuer of the securities and their creditworthiness , any changes to the rating of the security and any adverse conditions specifically related to the security , among other factors . also , we may evaluate the business and financial outlook of the issuer , as well as broader economic performance indicators . if this assessment indicates that a credit loss exists , the present value of cash flows expected to be collected from the security is compared to the amortized cost basis of the security . if the present value of cash flows expected to be collected is less than the amortized cost basis , a credit loss exists and an allowance for credit losses is recorded for the credit loss , limited by the amount that the fair value is less than amortized cost . any impairment that has not been recorded through an allowance for credit losses is recognized in other comprehensive income . any future deterioration in the fair value of an investment security , or the determination that impairment exists , may have a material adverse affect on future earnings . goodwill . goodwill is not subject to regular amortization but instead is required to be tested for impairment at least annually and possibly more frequently if certain events occur or changes in circumstances arise . in testing goodwill for impairment , we have the option to first assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying value . if , after assessing the totality of events and circumstances , we determine it is not more likely than not that the fair value of a reporting unit is less than its carrying value , then performing the impairment test would be unnecessary . however , if we conclude otherwise , it would then be required to perform the quantitative impairment test . in the quantitative impairment test , the fair value of each reporting unit is compared to its carrying amount in order to determine if impairment is indicated . if the estimated fair value exceeds the carrying amount , the reporting unit is not deemed to be impaired . if the estimated fair value is below the carrying value of the reporting unit , the difference is the amount of impairment . determining the fair value of a reporting unit requires a high degree of subjective judgment , including developing cash flow projections , selecting appropriate discount rates , identifying relevant market comparables , incorporating general economic and market conditions and selecting an appropriate control premium . story_separator_special_tag interest income on loans receivable increased by $ 16.1 million , or 4.1 % , to $ 410.9 million for the year ended december 31 , 2020 from $ 394.8 million for the year ended december 31 , 2019. this increase in interest income on loans receivable is attributed to increases in the average balance on loans receivable . the average balance increased by $ 1.549 billion , or 18.1 % , to $ 10.104 billion for the year ended december 31 , 2020 from $ 8.555 billion for the year ended december 31 , 2019. this increase is due primarily to the addition of $ 1.517 billion , at fair value , of loans related to the mutualbank acquisition and organic loan growth of $ 255.2 million . contributing to this organic loan growth was the origination of approximately $ 500.0 million of ppp loans . included in loan interest income for the year ended december 31 , 2020 is $ 3.1 million of accretion related to mutualbank loan purchase accounting and $ 5.7 million of accretion related to ppp fees , net of origination costs . partially offsetting this increase in average balances was a decrease in the average yield on loans receivable to 4.07 % for the year ended december 31 , 2020 from 4.61 % for the year ended december 31 , 2019 primarily due to the decrease in market interest rates . interest income on mortgage-backed securities increased by $ 746,000 , or 4.5 % , to $ 17.4 million for the year ended december 31 , 2020 from $ 16.7 million for the year ended december 31 , 2019. this increase is the result of an increase in the average balance of mortgage-backed securities by $ 250.0 million , or 39.1 % , to $ 889.7 million for the year ended december 31 , 2020 from $ 639.8 million for the year ended december 31 , 2019. this increase was primarily a result of investment securities received as part of the mutualbank acquisition as well as additional purchases utilizing excess cash from deposit growth during the current year . partially offsetting this increase was a decrease in the average yield on mortgage-backed securities to 1.96 % for the year ended december 31 , 2020 from 2.61 % for the year ended december 31 , 2019. this decrease in yield was partially due to the assumption of mortgage-backed securities from mutualbank with market yields lower than the existing northwest portfolio due to mark-to-market purchase accounting adjustments . in addition , new security purchases were made at lower yields due to decreases in market interest rates . interest income on investment securities remained relatively flat , decreasing by $ 200,000 , or 4.7 % , to $ 4.0 million for the year ended december 31 , 2020 from $ 4.2 million for the year ended december 31 , 2019. this decrease is the result of a decrease in the average balance of investment securities of $ 9.7 million , or 4.7 % , to $ 196.1 million for the year ended december 31 , 2020 from $ 205.8 million for the year ended december 31 , 2019 , which was primarily due to the maturity or call of government agency securities . the average yield on investment securities remained flat at 2.06 % for the years ended december 31 , 2020 and december 31 , 2019. dividends on fhlb stock decreased by $ 75,000 , or 7.1 % , to $ 1.0 million for the year ended december 31 , 2020 from $ 1.1 million for the year ended december 31 , 2019. this decrease is the result of decreases in the average yield on fhlb stock which decreased to 4.50 % for the year ended december 31 , 2020 from 7.29 % for the year ended december 31 , 2019. the fhlb of pittsburgh recently decreased yields on required stock holdings in reaction to lower market interest rates . slightly offsetting this decrease was an increase in the average balance on fhlb stock by $ 7.3 million , or 50.5 % , to $ 21.8 million for the year ended december 31 , 2020 from $ 14.5 million for the year ended december 31 , 2019 primarily due to fhlb stock acquired and retained from mutualbank . required fhlb stock holdings fluctuate with , among other things , the utilization of our borrowing capacity as well as capital requirements established by the fhlb . interest income on interest-earning deposits increased by $ 119,000 , or 19.8 % , to $ 719,000 for the year ended december 31 , 2020 from $ 600,000 for the year ended december 31 , 2019. this increase is attributable to an increase in the average balance of interest-earning deposits . the average balance increased by $ 497.4 million to $ 520.7 million for the year ended december 31 , 2020 from $ 23.3 million for the year ended december 31 , 2019 due to excess liquidity from recent deposit inflows . partially offsetting this increase was a decrease in the average yield on interesting-earning deposits to 0.14 % for the year ended december 31 , 2020 from 2.54 % for the year ended december 31 , 2019 , as a result of the federal reserve decreasing their targeted federal funds rate . interest expense . interest expense decreased by $ 14.6 million , or 25.6 % , to $ 42.3 million for the year ended december 31 , 2020 from $ 56.9 million for the year ended december 31 , 2019. this decrease in interest expense was primarily due to the decline in the average cost of interest-bearing liabilities which decreased to 0.49 % for the year ended december 31 , 2020 from 0.82 % for the year ended december 31 , 2019. this decrease resulted from decreases in the interest rates paid on deposits and borrowed funds in response to decreases in market interest rates . partially offsetting this

