NEW YORK ( TheStreet) - Iron ore production at BHP Billiton ( BHP) for the June quarter jumped 16% year over year against Rio Tinto's ( RTP) 2% decline . BHP achieved this output increase following a production ramp up at its Samarco iron ore mine.For the quarter, BHP's production of crude oil, alumina, silver, and metallurgical coal were up 21%, 9%, 6%, and 16%, respectively on a year-on-year basis. In contrast, natural gas, copper and uranium output declined 6%, 5% and 38%, respectively. Gold production, down 25%, weighed heavily on the firm's quarterly earnings, as the yellow metal's prices climbed nearly 30% year over year during the period. BHP remains cautious on the short-term outlook for the global economy. "Uncertainty surrounds the near-term prospects for growth in the developed world as governments adjust fiscal policies following a period of significant stimulus and subsequent increase in sovereign debt levels. Within China, measures introduced to reduce growth to more sustainable levels means volatility in commodity end-demand is likely to persist. BHP Billiton sees these measures as a normal continuation of China's economic management policies," BHP noted in the production report. Rio Tinto is also wary about the short-term outlook. "In recent weeks, fears about a possible double-dip recession in OECD countries and a slight slowdown in Chinese growth have led to some weakening in sentiment. We believe this pattern of volatility in the global economy is set to continue," said CEO Tom Albanese in a statement issued last week. Shares of BHP and Rio Tinto closed higher by 1.10% and 1.95%, respectively, in Australia. BHP has seven buy, two hold, and no sell ratings, while Rio has seven buy, three hold, and no sell ratings as per TheStreet's Analyst ratings guide. At $69.10 on the NYSE, BHP is currently trading at a price-to-earnings ratio of 14.8, higher than Rio's 7.7. In comparison, Vale ( VALE), Alcoa ( AA) and Freeport-McMoRan Copper & Gold ( FCX) are trading at PE ratios of 8.4, 22.8 and 8.5, respectively.