<prompt> Human: Im in a situation where I have a reasonable amount of cash that has been sitting on the side for the past year or so, and needs to make its way back into the stock market. Hypothetically, lets say theres 100k and its all inside a tax advantaged account IRA or Roth IRA.Does it make more sense to invest this all at once, or spread it out over a few months i.e. 13 each month for 3 months? Im notoriously bad at timing buysell decisions without trying to; it just seems to happen that way. Assistant: Do you want to maximize potential growth or hedge your risk against market downswings?Human: Yes? I am concerned that the market is a little high at the moment, but that kind of thinking is part of what brought me to this position. Im leaning toward the 13 each month for 3 months. So I guess the answer is Im more concerned about hedging my risk.  <response>: Its possible that the market is currently at the top of a bubble, that it will crash and fail to recover for years. If you fear the possibility, split your money into tenths and invest it over the next year or so. This will protect you against any weird market movement between now and then. However, as Boglehead said above, youre likely losing out on long-term appreciation on average when you do this sort of averaging. 