Replies

Several sources suggest you're wrong. Notice in the chart below a 1km diameter meteor is given a 75,000 Megaton kinetic equivalency.

Table 1 - Risk of direct impact for a given location

Diameter	Kinetic Energy	Area Devastated	Average. interval (years)
(m)	Mt TNT	sq km	Earth	"City"	Inhabited Region & Expected Death toll
50	10	1900	100 yr	30 million yr	900 yr 1 million
100	75	7200	1000 yr	70 million yr	8000 yr 3 million
200	600	29 000	5000 yr	90 million yr	30 000 yr 14 million
500	10 000	70 000	40 000 yr	290 million yr	180 000 yr 30 million
1 km	75 000	200 000	100 000 yr	260 million yr	290 000 yr 60 million
2 km	1 million MT	-	1 million yr	-	1 million yr 1.5 billion
All*			90 yr	14 million yr	800 yr

*All = 1/ ( 1/T₅₀+ 1/T₁₀₀ + 1/T₂₀₀ + 1/T₅₀₀ + 1/T₁₀₀₀) on the basis that probabilities are independent and span the range of asteroid sizes.

# See Appendix for calculation of risk to inhabited regions and predicted death toll.

An impact by a 2km diameter stony asteroid is thought to be at the threshold of a global catastrophe and the "damage" would go well beyond the area of direct devastation. It has been estimated that one quarter of the world's population could die from starvation and other indirect effects due to such an impact, which is thought to have an average interval of 1 million years (Morrison and Chapman 1995).