These are the typical questions investors often ask. These are called 'timing the market', 'trading actively', or a more debatable phrase: 'short-term investing'. To time the market is everybody's self- acknowledged skill and everybody's dream. But Buffett had lent us his wisdom in the Chairman's Letter in 1996: 

"Inactivity strikes us as intelligent behavior. Neither we nor most business managers would dream of feverishly trading highly-profitable subsidiaries because a small move in the Federal Reserve's discount rate was predicted or because some Wall Street pundit had reversed his views on the market. Why, then, should we behave differently with our minority positions in wonderful businesses?" 

Therefore, we did a light research to prove whether inactivity (long-term investing, or longer holding period) gains more than feverishly trading (short-term investing, or shorter holding period). We use the widely-referenced S&P 500 Index as the research object. We also use JCI Index and S&P 500 Index in IDR terms, since most of our readers reside in Indonesia. You will also notice that we emphasize 'dividend reinvestment', an important-but-often-neglected feature in investment. You may jump directly to the conclusion in the back, but first please do enjoy the frequency distribution graphs, and observe the shifts in return frequency from 1-year, 3-year, 5-year to 10-year holding period. 

If you aren't willing to own a stock for ten years, don't even think about owning it for ten minutes. 

- Warren Buffett, 

We gather end-of-month price of S&P500 (SPX), Jakarta Composite Index (JCI) and S&P500 in Rupiah (SPX in IDR, Indonesian local currency) terms so it is more relevant and useful for our reader in Indonesia. 

Calculating 1-year, 3-year, 5-year and 10-year return for each month; Add dividend reinvestment to the calculation. 

(Notes: Most people do not care of how big their dividend accumulation is, and how this tremendous wealth is silently taken away by some professional money managers in Indonesia by charging high management fees.)

Creating a frequency histogram, where x-axis is the return, and y-axis is the number of occurrence for each return 

Observing the occurrence of negative (red) and positive (blue) return for each time frame.

The longer holding period, the higher potential returns, and the bigger chance to get them. 

In this research, the number of observation is in months. It means you can start investing at any time during a year, and still have bigger chance to get positive returns, as long as you hold your portfolio longer. 

This research does not apply to a single stock. It is important to have a portfolio of stocks, not just a single stock. 

Be aware of your dividend. If reinvested, it counts a lot in the long-run.