Well, congratulations on at least trying to figure that out. When I was 16 I was just trying to figure out how to get a girl to go out with me on a date.
I'm 62 and have been planning my retirement for 40 years. Every year, for 40 years I have met with the same attorney and accountant, making short term plans for how much I could put away in various investment vehicles. You can only imagine how many times the laws have changed over that time. For a few years I could not invest in a tax deductible IRA because I had a corporate pension fund, then for a few years I could, then I couldn't.
Every year various "loop-hole" investments were closed up to me, as the IRS decided they wanted more of my money. When I started working, the idea of making enough money to trigger the "Alternative Minimum Tax", was a joke. But decades of inflation without raising the ceiling on AMT, and now it's not a joke.
Every year for 40 years we'd discuss what "may" happen and how that might affect my plans. The bottom line is that I, and my advisors were wrong as often as we were right.
My advice: pay attention to what is going on, but don't fret about it. If you are lucky, you'll develop some sort of "feel" for where things are going. Trying to figure out now, where things will be in 20, 30, or 40 years? You probably won't.
Set some long term goals, medium term goals, short term goals, and then figure out what you can do today and tomorrow and the day after that to move you along the road you think you'd like to travel. Don't ever feel like the road you picked when you were 16, or 18, or 25, or any age is the road you have to stay on, just because you chose it.
Don't get so focused on the destination that you ruin the journey. And the best advice I ever got was from my Mom, "find a skill. Be of use, and you'll never starve"...she was right about that.
Best of luck.