Elon Musk memo suggests Twitter worth less than half of what he paid for it

Twitter is worth less than half of what Elon Musk paid for it six months ago having lost more than $20bn (£16.4bn) in value, according to calculations based on a leaked memo from the billionaire.

Generally used as way to incentivise employees, stock grants are an opportunity to buy shares that cannot be sold until a set point in time, as opposed to stock options, which - depending on the conditions applied - can be more flexible. The aim is to encourage staff to reach a set valuation by a point in time so that they can sell their shares for cash.

The memo suggests the model would be similar to that which Musk, who also runs Tesla, has adopted at SpaceX, another of his companies, which allows staff to sell shares back to it.