Historical Spare Capacity

It's simple enough to find charts of this, but the actual numbers are MIA. The EIA provides them for the previous decade or so via their Short-Term Energy Outlook, select "11. OPEC Surplus Crude Oil Production Capacity" under the "Figures" section. It's a given that only OPEC have any SC these days, natch. You have your choice of graph or .xls. But STEOs I've checked out from the 80s/90s just seem to have graphs and helpful statements like "Significant excess oil production capacity is expected to exist in the OPEC member nations throughout the forecast period." They provide a table for International Petroleum Balance, but this juxtaposes production with product supplied, noting the difference between the two, which is neglible, at < 1 mb/d generally; good for tracking how much went into stock draws, but not spare cap. Stuart Staniford tackled this approach in Refining the Plateau, a 2006 TOD post, by noting the difference between production and refining capacity in the 2005 BP Stat Review, yielding this:

Two problems present themselves here, firstly that BP's production numbers are ex biofuels, and have late become quite divorced from other All Liquids measures; also this approach yields what seem to be quite implausible figures, like 2.1 mb/d for 2006, whereas EIA gives 1.42 mb/d. Numbers for the 80s from BP are even more out there, peaking at 18.7 mb/d in 1981. There was a lot of unused supply back then, but this deviates sharply from other estimates you see in graphs from professional research firms and government agencies.

A site I've found very useful is John Williams's WTRG, and its Oil Price History and Analysis page. This graph isn't there anymore, perhaps it's still stuck away in a corner of the site somewhere:

Well, I'll put my trust in John to deliver the goods, and have reverse engineered his numbers:

1970 4.4
1971 4.8
1972 4.8
1973 3.2
1974 4.5
1975 8
1976 4.7
1977 5.2
1978 7
1979 4.2
1980 6.1
1981 7.7
1982 9.8
1983 10.3
1984 9.6
1985 10.8
1986 8.8
1987 8.7
1988 6.7
1989 5.9
1990 3.3
1991 1.2
1992 2
1993 3.1
1994 3.2
1995 3.2
1996 3.2
1997 3.5
1998 3.6
1999 5.4
2000 3.6
2001 4.9
2002 6.2
2003 1

I made a graph of these numbers and superimposed it on John's, revealing a pretty tight fit. Close enough for government work, as my Dad used to say. Here's what the EIA have in the latest STEO:

2000 3.0
2001 4.1
2002 5.5
2003 1.9
2004 1.3
2005 1.0
2006 1.4
2007 2.1
2008 1.5
2009 4.3
2010 4.7
2011 4.7
2012 4.2

I rounded down to the 10th decimal place here, FYI. They expect a 200 kb/d build for this year. Yay! Their own data shows only 1.4 mb/d shut in from the July 2008 absolute peak, so the 2.8 mb/d difference is fresh oil, 1.2 mb/d from Khurais, which we are led to believe will provide 10 times its historic output. Wonder if that's ever been pulled off before...

Spare Capacity in the papers:

"Nearly 8 mb/d, compared to about <1.5 mb/d before the Middle East war last October" - The Milwaukee Journal - Dec 9, 1974

"In less than two years, it is doubtful that OPEC will have any spare capacity" - The Montreal Gazette - Nov 3, 1979

<3.2 mb/d from OPEC, less on a sustained basis, according to State Department rep: St. Petersburg Times - Nov 16, 1979

3.5 mb/d from KSA: The Milwaukee Journal - May 24, 1982

8 mb/d total from Arabian Gulf countries, according to Exxon rep: The Leader-Post - May 17, 1984

Herald-Journal - Jun 25, 1987e 10 mb/d according to DOE rep, 1 mb/d before the 70s oil crises, warns of SC drying up by the 90s without reserves additions.

2 mb/d, down from 14 mb/d in 1986, according to employee of DC firm the Petroleum Financial Company: NYT, March 6 1990

4% of total, i.e. ca. 2.5 mb/d: The Telegraph-Herald - Apr 9, 1990

Few solid figures are available in the 90s; starting in the middle of that decade more online web based commentary is available, as opposed to the earlier format of scanned newspapers; beginning about 10 years ago papers seem to start directly quoting the IEA's OMR and the like.