Backtesting???

Backtesting is the general method for seeing how well a strategy or model would have done ex-post. Backtesting assesses the viability of a trading strategy by discovering how it would play out using historical data. If backtesting works, traders and analysts may have the confidence to employ it going forward.

Investing/trading course trainers or FAs love to use backtesting data or past performance as marketing tool or snake oils to sell! You see how much you can make! Don't wait! You will regret!

But; Uncle8888 realized on the ground is NOT that simple! Nobody know how future will turn out! AI knows better?

The Past is NOT the Present and the Present is NOT the Future - CW8888

Is there any hints or backtesting data to show that we one day will have to wear Mask for such long time?

First batch of surgical masks; Uncle888 bought from ex-colleague's Vietnamese friend at $18/box and second batch $30+(then the price shot up to $50+, heng ah! Already bought enough at 30+), $20+, $10+ at pharmacy and recently free box from vaccination centre! LOL!