the 1929 crash took 48% off the dow in ten weeks. that is not what ruined anybody. what ruined people was the 40% rally that came next. the peak was 381.17 on 3 september 1929. by 13 november it was 198.60. then it went up. from that november low the dow climbed about 40% into april 1930. the panic was declared over, the headlines said the worst had passed, and the money came back in. the final low was 41.22, in july 1932. which means anyone who bought the november 1929 bottom, the actual low of the crash everybody remembers, was down 79% by the time it finished. here is the part almost nobody takes from this, because everyone stops at the crash itself. the first decline removes the people using borrowed money. it is fast, it is mechanical, and it does not require anybody to change their mind. the broker sells whether you agree or not. the rally is what brings everyone else back. it arrives with headlines saying the worst is over, and while it is happening it is indistinguishable from a recovery. the second decline takes the capital that returned voluntarily. peak to trough the dow lost 89%. to undo an 89% loss you need a gain of 809%. not 89%. that is the number worth carrying around. not how much you can make, but how much you can afford to be wrong by. down 20% needs 25% to get back. down 50% needs 100%. down 89% needs 809%. almost nobody has that column in front of them when they size a position. i put it in a sheet next to your own position sizes. DM me "809".