The direct benefit of North Sea oil and Gas is most obviously expressed as its contribution to national output. This grew dramatically from 1975 to reach a peak of around 6.9% of gross value added (GVA) in 1984, followed by an equally dramatic fall in subsequent years (see Appendix 13.1). The collapse of oil prices to a low of $10 in 1986 was a major contributory factor (see Appendix 13.2), but oil production also fell significantly to 1990 (see Appendix 12.4). As noted in Chapter 8 investment in the North Sea grew dramatically in the 1970s (see Appendix 8.5), and constituted a major element in total UK industrial investment (see Appendix 22.1). The historic behaviour of gross and post-tax net industry income (at 2006 prices) is shown in Appendix 13.3. Total Government revenues (also at 2006 prices) are shown in Appendix 13.4. These revenues (in real terms) attained very high levels in the first half of the 1980s, reaching £17 billion in 1981/82, £19 billion in 1982/83, over £20 billion in 1983/84, and peaking at nearly £27 billion in 1984/85. Thereafter they declined dramatically to just over £10 billion in 1986/87 and £2 billion in 1991/92.