How often do Vanguard Target Date Funds rebalance?

I’ve been doing a lot of research lately on portfolio rebalancing and it got me wondering about Vanguard’s rebalancing strategy for its own target date funds.  After reviewing the fund’s prospectus, I decided to give Vanguard a call directly using their customer service line and ended up speaking with a representative named Robert.  I asked Robert two primary questions:

How often does my target date fund (VFIFX) rebalance?  Robert first searched through the prospectus and couldn’t find anything there so he had to place me on hold and speak with another department.  When he came back he told me that Vanguard rebalances daily just by properly managing the money coming into the fund from new investors/re-investors and the money going out of the fund from withdrawals.  He also told me that if the portfolio skews more than 2 or 3 percent from its target allocation, the fund will actively buy or sell shares of its underlying holdings to rebalance.  I pressed Robert on this point by asking him if it was an automatic 2% trigger or if the fund would only make an active adjustment during set time periods.  In other words, did the manager check the fund every quarter and only rebalance if the assets were more than 2% off, or would the manager rebalance any time the the assets were 2% off – even if it meant making trades every other day (like in a volatile market)?

Robert’s response to this was interesting – although in retrospect unsurprising.  He said that Vanguard does not release that information because of the potential for abuse.  If it was public knowledge that Vanguard rebalanced its funds on certain dates, then traders could take advantage of that fact by manipulating the price of the underlying funds that the VFIFX would have to buy in order to rebalance (In this case, VFIFX has 3 underlying funds: the Vanguard total stock market index, the Vanguard total international stock market index, and the Vanguard total bond index).  I’m not entirely sure how someone could benefit from this knowledge, but I’m guessing it is related to the ways in which a hedge fund manager can manipulate stock prices.

Does my target date fund shift its asset allocation on a continuous basis?  Robert pointed me to the graphic on the Vanguard Target Retirement fund site (which I’ve also linked to in previous posts).  When you click on a fund under the heading  “Decide which fund is right for you,” you will see a graphic similar to the one below.  This particular graphic corresponds to the 2050 fund (VFIFX).

As you move the slider left or right, it will tell you the asset mix that the fund will have at that time.  My question to Robert was whether the asset allocation changed continuously as the graph indicates (meaning a smooth line), or if it changed at stepped intervals – like every five years that corresponds to the Target fund offerings (there is no target date fund for 2051).  Robert said that the graphic essentially represented how the allocations would change, but didn’t go into much further detail.

I took a screenshot below showing the allocation change that occurred by moving the slider slightly to the right.  From what the graph tells me (by playing with the slider for a few minutes) the asset allocation changes every year. Presumably that is the answer – Vanguard Target Date Funds adjust their allocation every year.  Although, conceivably Vanguard could adjust the allocation daily by hundredths of a percent to create an even more continuous risk reduction instead of adjusting just once a year.