The Organization of the Petroleum Exporting Countries was founded in 1960 to strengthen the bargaining power of producing countries, then mostly Gulf-based, relative to the so-called Seven Sisters multinational oil companies, which dictated global output and price levels at the time. OPEC flexed its muscles with a vengeance in the 1970s, driving crude prices up more than tenfold. Today the 12-nation cartel is on the defensive. The influx of North American shale oil onto the global market sent crude prices skidding sharply last year; Saudi Arabia accelerated the decline by deciding to stop playing swing producer and instead keep its wells pumping to regain market share. Although the benchmark Brent crude has rebounded somewhat in recent weeks, it is still down more than 45 percent from its summer 2014 peak, at a little under $59 a barrel on February 24. The past eight months have been brutal for countries whose livelihoods depend on their oil reserves. Here is a country-by-country breakdown of how each OPEC member has fared during that period.