if during the 20 year time frame, say 4 year bear, 3 year bull, (roughly). if this 20 year started with a bear,

4 + 3 + 4 + 3 + 4 + 2 (2.67 bull, 3 whole bear market)

if starts with a bull, 3 + 4 + 3 + 4 + 3 + 3 (3 whole bull, 2.75 bear)

say in bull market, return is 50%, bear return is -20%

if you have 10k, at the end of the 20 year, you have:

if you have 10k, at the end of the 20 year, you have:

if start with bear market, if you don't time the market, you will end up with

10 (0.8)^3 (1.5)^2 (1.5 * 2/3) = 11.52k

if start with bull market, if you don't time the market, you will end up with

10 (1.5) ^3 (0.8)^2 (0.8 * 3/4) = 12.96k

if you time the market, but timing is not perfect, (nobody can), so you get 40% return on the bull market, and you avoid loss on the bear market.
for the first case, you got 2.67 bull
10K (1.4)^2.67 = 24.55k

for the second case, you get 3 whole bull
10k (1.4)^3 = 27.44k

so now you can tell the difference.

for individual invester, we do not have 50 years. If you have been through the last dot come crash, and lost 80% of the money, you may never get the chance to come back.

Legitimate scam, that's what many market ananysis or MF manager want you to believe, so-called invest in long term. for many of us here, we are young, we dont have too much money. we have enough time to start from 0, but for many others, this is not the case.

Why do I say 20 year time frame, most of us will not start serious investing until early 30, this is when you have a stable job, and start to make significant more than you spend. say you invest till some time in early or late 50s, you've got roughly 20-25 years.