Venezuela's crude oil sales tothe United States fell for a second month in a row in December,knocking the year's average to 593,047 barrels per day (bpd),the lowest annual level since 1991, according to Thomson Reuterstrade flows data.A severe production drop in the South American country hashurt its oil exports and domestic refining, and worsened aneconomic recession now entering into its fifth year. Venezuela'sstate-run oil company PDVSA is mired in a widespread corruptioninvestigation that has stalled decision making. Financial sanctions on Venezuela imposed last year by U.S.President Donald Trump's administration have particularlyaffected PDVSA's oil flows to and from the United States as thecompany and some of its customers struggle to get commercialcredit for transactions.The International Energy Agency, which coordinates theenergy policies of industrial nations, and several analysisfirms expect Venezuela's crude output to lose another 500,000bpd this year due to lack of investment, mounting debts,sanctions, a brain drain caused by low salaries and a newmanagement with no experience in the oil industry.In total, the United States received 419 crude cargoes ofVenezuelan crude last year versus 530 cargoes in 2016, accordingto the data. The largest receivers were PDVSA's refining unitCitgo Petroleum and Valero Energy Corp.Chevron Corp and Phillips 66 also importedcargoes during the year, according to the data. Refining firmPBF Energy Inc stopped receiving direct supplies ofVenezuelan crude from PDVSA in October after contractdisagreements. PDVSA and its joint ventures mainly sold diluted crude oil(DCO) to U.S. customers last year, a grade that mixes Venezuelanextra heavy oil with imported heavy naphtha.The 2017 volumes reflected lower exports in recent months.Since September, shipments to the United States have notsurpassed 550,000 bpd, well below the average of earlier months.In 2016, Venezuela exported 718,365 bpd of crude to theUnited States from an oil production of 2.466 million bpd.Production in November - the latest number available - was 1.837million bpd, according to figures published by OPEC. The following is a table of Venezuelan crude sales to theUnited States from PDVSA's ports and terminals, according to theReuters data: PeriodExports Number of (bpd) cargoes December392,710 24 November475,165 28 October 541,130 33 September 488,165 30 August660,235 38 July638,325 3i6 June491,335 29 May 698,225 42 April 641,000 42 March 561,710 40 February667,035 37 January 675,160 40 2017593,047 419 2016718,365 530 2015772,880 582 2014733,000 N.A. 2013755,000 N.A.(Reporting by Marianna Parraga; Editing by Lisa Shumaker)Read full news