每日钉一下（个人投资的四类常见资产，牛熊周期分别有多长？）

Group 1 - The article highlights that most investors are familiar with stock index funds but have limited knowledge about bond index funds and their investment strategies [2] - A free course is offered to educate investors on how to invest in bond index funds, along with supplementary materials like course notes and mind maps for efficient learning [2] Group 2 - The article discusses the market cycles of different asset classes, categorizing them into four main types based on their bull and bear market cycles [5] - Bond assets typically have a bull-bear market cycle of 3-5 years, aligning with interest rate cycles [5] - Stock assets experience longer bull-bear cycles, with shorter cycles lasting 3-5 years and longer cycles extending to 7-10 years [5] - Gold also has a bull-bear market cycle comparable to stocks, with a notable 5-year bear market from 2011 to 2016 [5] - Real estate has the longest bull-bear market cycle, averaging 15-20 years, with the last bear market bottoming in 2008 and a bull market starting around 2018 [5]