Utilize your financial knowledge, give your answer or opinion to the input question or subject . Answer format is not limited.

Can saving/investing 15% of your income starting age 25, likely make you a millionaire?
The really simple answer is that compound interest is compound not linear.  Money invested for longer earns more interest, and the sooner you start investing, the longer it has to earn interest.  These ideas come out of pension investment where 65 is the usual retirement age and what you invest in the 1st ten years of your pension (or any other compound interest fund) accounts for over 50% of what you will get out. 25 to 65 is forty years and $100 invested at 7% for 40 years is $1400.  $100 invested every year for 40 years the pot would be worth just under $20,000. At 30 years, it would be worth under $10,000, and at 20 years it would be worth only $4099.  If you double your investment amount every 10 years you would have invested $15700, and the pot would be worth $45,457. Do exactly the same but starting at 35 instead of 25 and your pot would only be worth $14,200.