Venezuela’s only source of cash is quickly dwindling as the country faces mounting unpaid bills, violent political protests and citizens starving due to food shortages. Oil makes up nearly all of Venezuela’s exports, and with the country in a full-blown crisis, oil is only thing it can sell. But production is down to its lowest levels since 1989 — excluding an oil strike in 2002 — according to data compiled by Rice University professor Francisco Monaldi. Production has declined 10 out of last 11 years, according to BP statistics. And in the first half of this year, it was down sharply, 12%, compared to the same time last year, OPEC numbers released on Wednesday show. Central to its production problem is that oil service providers, such as Halliburton and Baker Hughes, have cut back on pumping out oil until President Nicolas Maduro pays them back for millions of dollars […]