Total US rig countAccording to oilfield service company Baker Hughes BHI, there were 859 active oil and gas rigs in the United States in the week ending June 12, 2015, nine less than the previous week ending June 5.With last week’s fall, the average four-week US rig count drop was seven, the same as the previous four weeks to June 5. The rig count drop averaged eight in the four weeks to May 29, and 12 in the four weeks to May 22. So, the rate of decline is clearly slowing down.Enlarge GraphRig count is lowest since January 2003The US rig count experienced an uptrend throughout most of 2014. But that trend reversed with 27 consecutive weeks of falling rig counts. With last week’s fall, the US rig count hit its lowest level since January 2003. The fall in onshore rig count led the week’s figures.May’s average rig count of 889 represents a decline of 87 from 976 active rigs in April.The total US rig count hit 2,031 in September 2008, the highest since July 1987, according to Baker Hughes. In September 2014, the average rig count came close to that record, reaching 1,931. Since September last year, ~56% of the rigs have been idled.Energy companies, including Gulfport Energy GPOR, Linn Energy LINE, Ultra Petroleum UPL, EOG Resources EOG, and Newfield Exploration NFX, have upstream operations. A falling rig count typically leads to a slowdown in production growth and possibly even a decline in production. Falling production will negatively affect upstream master limited partnerships like Vanguard Natural Resources VNR.Ultra Petroleum accounts for 1.15% of the SPDR S&P Oil & Gas Exploration & Production ETF’s XOP total market capitalization. Gulfport Energy accounts for 0.25% of the iShares U.S. Energy ETF IYE.Why have US rig counts been falling for so long? We’ll discuss this in the next part of this series.