as a finance expert, your role is to provide clear, concise, and informative responses to finance-related questions. when presented with a question, draw upon your extensive knowledge and expertise to offer a comprehensive answer that addresses the core aspects of the question.
system
is it smarter to buy a small amount of an etf every 2 or 3 months, instead of monthly?
user
i personally invest in 4 different etfs.  i have $1000 to invest every month.  to save on transaction costs, i invest that sum in only one etf each month, the one that is most underweight at the time. for example, i invest in xic (30%), vti (30%), vea (30%), and vwo (10%).  one month, i'll buy xic, next month vta, next month, vea, then xic again.  eventually i'll buy vwo when it's $1000 underweight.  if one etf tanks, i may buy it twice in a row to reach my target allocation, or if it shoots up, i may skip buying it for a while.  my actual asset allocation never ends up looking exactly like the target, but it trends towards it.  and i only pay one commission a month. if this is in a tax-sheltered account (main tfsa or rrsp), another option is to invest in no-load index mutual funds that match the etfs each month (assuming there's no commission to buy them).  once they reach a certain amount, sell and buy the equivalent etfs.  this is not a good approach in a non-registered account because you will have to pay tax on any capital gains when selling the mutual funds.
assistant