• There should be ~950 NEOs with H<18 and ~850 with diameter larger than 1 kilometre, with a<7.4 AU
• The current observational completeness of this population is slightly smaller than 50%
• With the current surveys, the H<18 objects will reach 90% observational completeness in ~60 years
• Objects with H<18 NEO should collide with the Earth (on average) once every 500,000 y. The energy produced by these impacts is equivalent to 46,000 megaton TNT
• Collisions with energies larger than 1,000 megaton are caused by NEOs with H<20.5; they stike the Earth (on average) every 63,000 years
• The efficiency of a NEO survey strongly depends on the heliocentric distance of the observatory. A space survey onboard a spacecraft placed at Mercury's or Venus's heliocentric distance would offer a tremendous advantage with respect to a survey conducted from the ground or onboard a geocentric satellite

Recommendations:

• Governments should not be satisfied with the current facilities dedicated to NEO searches. Resources should be allocated to increase both the limiting magnitude and the sky coverage, in order to improve the detection efficiency.
• The Spaceguard goal should be extended to include the NEOs with H<20.5 in order to protect the society from these frequent and dangerous impactors
• Space agencies should seriously consider the possibility of developing a dedicated space-based NEO survey, onboard a spacecraft placed in the inner solar system