Pension funds. The company you work for will give X% of your salary each month to Willis Towers Watson or whoever, who invest huge sums of money on behalf of p

Pension funds. The company you work for will give X% of your salary each month to Willis Towers Watson or whoever, who invest huge sums of money on behalf of people like you. Then you move jobs or the start-up fails or whatever, but your old money is still with Towers Watson, hopefully earning a decent return. You contribute to a pension in your new job too. When it comes to retiring, you cash in your contributions from the pension fund (possibly having done some amalgamating and tidying up from the various jobs you've had) for some class of annuity and possibly a lump sum. All going well, it should be enough to live on in retirement. If you're working and aren't contributing to a pension, I would strongly recommend it.