What inherent limitation results in the current catalog of known exoplanets being biased?

Answer

The catalog is heavily weighted toward worlds whose orbits are oriented perfectly for observation via transit.

The visibility of methods like transit detection depends heavily on orbital geometry. Worlds orbiting edge-on to our line of sight are much easier to find using transit monitoring, leading to an observational bias in the resulting catalog.

What inherent limitation results in the current catalog of known exoplanets being biased?
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