Note:
The slope of the regression line is $126.03 billion of GDP per Quadrillion Btu used, or $126.03/1000 Btu.
Notes:
1. The slope of this regression line is $0.1116/Btu or $111.60/1000 Btu.
2. A few developed countries have achieved efficiencies of 1.5 times the average slope.
3. In both plots, GDP is roughly proportional to the Btu used, indicating that energy is needed to obtain a high GDP.
CIA World Factbook Data for Countries of at least 15 Million Population
Sorted by Btu used per person per year.
Total Energy Energy  GDP/
Energy Efficiency PPP Births Used/ capita
Dominant Used GDP/Quad GDP /1000 Pop. person/yr $US/ Test=1.5
No. Country Culture Quad Btu $Bill/Quad $Billions pop/yr Millions Btu/capita person/yr *slope
1 Canada Christian 13.713 81.24 1,114.00 10.78 33.10 414,296 33,657 69,353
2 United States Christian 101.429 121.86 12,360.00 14.14 298.44 339,859 41,415 56,892
3 Australia Christian 5.335 119.98 640.10 12.14 20.26 263,283 31,588 44,074
4 Netherlands Christian 4.159 120.18 499.80 10.90 16.49 252,186 30,307 42,216
5 Saudi Arabia Muslim 6.191 54.59 338.00 29.34 27.02 229,143 12,509 38,359
6 Russia Orthodox 30.548 52.02 1,589.00 9.95 142.89 213,784 11,120 35,787
7 Taiwan Buddhist 4.477 140.99 631.20 12.56 23.04 194,341 27,400 32,533
8 France Christian 11.457 158.51 1,816.00 11.99 60.88 188,199 29,831 31,505
9 Korea, South Buddhist 9.151 105.48 965.30 10.00 48.85 187,344 19,762 31,361
10 Germany Christian 14.974 167.23 2,504.00 8.25 82.42 181,671 30,380 30,412
11 Japan Buddhist 23.057 174.26 4,018.00 9.37 127.46 180,894 31,523 30,282
12 United Kingdom Christian 10.244 178.64 1,830.00 10.71 60.61 169,015 30,193 28,293
13 Spain Christian 6.539 157.36 1,029.00 10.06 40.40 161,868 25,472 27,097
14 Kazakhstan Muslim 2.383 52.16 124.30 16.00 15.23 156,448 8,160 26,189
15 Italy Christian 8.463 200.65 1,698.00 8.72 58.13 145,573 29,209 24,369
16 Ukraine Orthodox 6.645 51.23 340.40 8.82 46.71 142,249 7,287 23,812
17 South Africa African 5.269 101.20 533.20 18.20 44.19 119,238 12,067 19,960
18 Venezuela Christian LA 2.971 51.73 153.70 18.71 25.73 115,472 5,973 19,330
19 Malaysia Muslim 2.601 111.55 290.20 22.86 24.39 106,679 11,900 17,858
20 Poland Christian 3.798 135.33 514.00 9.85 38.54 98,561 13,338 16,499
21 Iran Muslim 6.683 84.04 561.60 17.00 68.69 97,289 8,176 16,286
22 Uzbekistan Muslim 2.320 20.80 48.24 26.36 27.31 84,948 1,767 14,220
23 Romania Orthodox 1.720 106.74 183.60 10.70 22.30 77,119 8,232 12,910
24 Chile Christian LA 1.236 151.39 187.10 15.23 16.13 76,598 11,596 12,822
25 Argentina Christian LA 2.924 177.18 518.10 16.73 39.92 73,246 12,978 12,261
26 Mexico Christian LA 6.974 152.99 1,067.00 20.69 107.45 64,909 9,930 10,866
27 Thailand Buddhist 3.643 153.91 560.70 13.87 64.63 56,366 8,675 9,436
28 Turkey Muslim 3.772 151.64 572.00 16.62 70.41 53,570 8,123 8,968
29 Brazil Christian LA 9.717 160.13 1,556.00 16.56 188.08 51,665 8,273 8,649
30 China Buddhist 64.041 138.33 8,859.00 13.25 1,313.97 48,738 6,742 8,159
31 Iraq Muslim 1.298 72.52 94.10 31.98 26.78 48,448 3,513 8,110
32 Syria Muslim 0.888 81.46 72.33 27.76 18.88 47,026 3,831 7,872
33 Korea, North Buddhist 0.969 41.27 40.00 15.54 23.11 41,933 1,731 7,020
34 Algeria Muslim 1.351 172.65 233.20 17.14 32.93 41,017 7,082 6,866
35 Egypt Muslim 2.791 108.74 303.50 22.94 78.89 35,380 3,847 5,923
36 Colombia Christian LA 1.341 251.70 337.50 20.48 43.59 30,759 7,742 5,149
37 Peru Christian LA 0.673 244.46 164.50 20.48 28.30 23,775 5,812 3,980
38 Indonesia Muslim 5.521 156.79 865.60 20.34 245.45 22,493 3,527 3,765
39 Philippines Christian 1.614 279.62 451.30 24.89 89.47 18,040 5,044 3,020
40 India Hindu 19.141 188.66 3,611.00 22.01 1,095.35 17,475 3,297 2,925
41 Morocco Muslim 0.557 248.18 138.30 21.98 33.24 16,764 4,160 2,806
42 Pakistan Muslim 2.549 154.31 393.40 29.74 165.80 15,376 2,373 2,574
43 Vietnam Buddhist 1.235 187.97 232.20 16.86 84.40 14,636 2,751 2,450
44 Sri Lanka Buddhist 0.266 321.19 85.34 15.51 20.22 13,139 4,220 2,199
45 Nigeria African 1.461 119.18 174.10 40.43 131.86 11,078 1,320 1,855
46 Yemen Muslim 0.237 81.79 19.37 42.89 21.46 11,037 903 1,848
47 Mozambique African 0.206 126.62 26.03 35.18 19.69 10,443 1,322 1,748
48 Ghana African 0.218 250.10 54.45 30.52 22.41 9,715 2,430 1,626
49 Cote d'Ivoire African 0.170 167.67 28.52 35.11 17.65 9,634 1,615 1,613
50 Kenya African 0.293 126.88 37.15 39.72 34.71 8,436 1,070 1,412
51 Cameroon African 0.145 280.95 40.83 33.89 17.34 8,381 2,355 1,403
52 Bangladesh Muslim 1.159 262.64 304.30 29.80 147.37 7,862 2,065 1,316
53 Myanmar Buddhist 0.363 216.62 78.74 17.91 47.38 7,672 1,662 1,284
54 Sudan Muslim 0.288 297.04 85.65 34.53 41.24 6,992 2,077 1,171
55 Nepal Hindu 0.159 250.88 39.90 30.98 28.29 5,622 1,411 941
56 Madagascar African 0.100 164.22 16.36 41.41 18.60 5,357 880 897
57 Tanzania African 0.200 135.61 27.07 37.71 37.45 5,331 723 892
58 Uganda African 0.137 356.69 48.73 47.35 28.20 4,845 1,728 811
59 Congo, Dem. R. African 0.300 135.47 40.67 43.69 62.66 4,791 649 802
60 Ethiopia Muslim 0.338 186.04 62.88 37.98 74.78 4,520 841 757
61 Afghanistan Muslim 0.121 177.30 21.50 46.60 31.06 3,905 692 654
Sum or Average 422.521 130.72 55,230.06 22.36 5,922.24 71,345 9,326 11,943
Others 46.106 118.85 5,479.94 602.93 76,470 9,089 12,801
World 468.628 129.55 60,710.00 20.05 6,525.17 71,818 9,304 12,022
Sample/World, % 90.16 90.97 90.76
Total Energy Energy  GDP/
Energy Efficiency PPP Births Used/ capita
Dominant Used GDP/Quad GDP /1000 Pop. person/yr $US/
Culture Quad Btu $Bill/Quad $Billions pop/yr Millions Btu/capita person/yr
Correlations:
Quad Btu used 1.000 (0.153) 0.976 (0.326) 0.568 0.475 0.478
Energy Efficiency (0.153) 1.000 (0.066) 0.230 0.015 (0.437) (0.162)
GDP, $billions 0.976 (0.066) 1.000 (0.326) 0.641 0.408 0.489
Births/1000/yr (0.326) 0.230 (0.326) 1.000 (0.118) (0.621) (0.666)
Population 0.568 0.015 0.641 (0.118) 1.000 (0.058) (0.029)
Btu/person/year 0.475 (0.437) 0.408 (0.621) (0.058) 1.000 0.882
GDP/Capita 0.478 (0.162) 0.489 (0.666) (0.029) 0.882 1.000
Conclusion: 
Since only a few developed countries exceed 1.5 times the average slope, it seems wise to currently limit
energy efficiency between $170 and 200 billion/Quad. I have set the upper limit at $175 billion of GDP/Quad in my model.
Notes:
1. Energy consumption is best correlated with GDP as expected.
2. Btu/capita is best correlated with GDP/capita.
3. The US and Canada need to be more efficient.
4. US DOE EIA Table E.1  World Total Primary Energy Consumption (Quadrillion Btu), 1980-2004.
5. The average person consumes about 2,350 nutritional calories/day, or 2,350*365 = 857,750 nutritional calories/year.
     Since one nutritional calorie equals 1000 chemical calories, this equals 857,750,000 chemical calories/year.
     Since one Btu = 251,996 calories, the average person consumes 3,404 Btu/year as food. In poor countries,
     little machinery is used to grow food crops or to make products and GDP/Quad is high if food is omitted.