According to Oliver Tickell, not much:
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Numerous advantages for thorium as a nuclear fuel and for the LFTR design over conventional solid fuel reactors have been claimed. In this section we consider each of these claims in turn.
3.1 Abundance of thorium relative to uranium
Claim: Thorium is several times more abundant in the Earth’s crust than uranium.
Response: Thorium (232Th) is indeed more abundant than uranium, by a factor of three to four. But whereas 0.7% of uranium occurs as fissile 235U, none of the thorium is fissile. The world already possesses an estimated 1.2 million tonnes of depleted uranium (mainly 238U), like thorium a fertile but non-fissile material. So the greater abundance of thorium than uranium confers no advantage, other than a very marginal advantage in energy security to those countries in which it is abundant.