There are several ways to time the launch of a new exchange traded fund (ETF).
One is to strike while a sector is hot, pull in a lot of trend-following money
and accept that the fund's performance might be mediocre, since the hotter
the sector the more due it is for a correction. That's how it went for the
Market Vectors Junior Gold Mine ETF (GDXJ), which nearly doubled in its first
year of trading and is since down by more than half. (Full, painful disclosure:
I've ridden that train from beginning to end.)

Another approach is to launch when a sector is out of favor, accept that you'll
attract very little money up front but hope that good future performance will
draw investors later on. That's what Madison NJ Pure Funds has done with its
new Junior
Silver Miners ETF (SILJ).
As a group these miners have truly sucked (both operationally and as investments)
in the past couple of years, underperforming both silver itself and the overall
stock market. This has scared away the momentum players, while intriguing
contrarians and non-gold-bug value investors.
As with most small cap sectors, someone approaching silver juniors faces a
lack of good information and massive company-specific risk that cries out
for either months of in-depth research or immediate diversification. Which
is where ETFs come in. By offering instant exposure to 20 or 30 names, they
allow someone new to a sector to play while learning.
From this point of view SILJ has launched at just the right time. Its top
ten holdings are a mix of familiar and unfamiliar names, almost all of which
are closer to their 12-month lows than highs:

One of the downsides of introducing an ETF in an out-of-favor sector is that
it won't have much initial trading volume. As this is written on the morning
of February 8, SILJ literally hasn't seen a single trade. So this is not something
you buy "at the market," since "the market" might be 30% higher than the next
trade. Instead, choose a reasonable price and put in a good-until-cancelled
bid -- and then watch it to make sure nothing crazy happens in the meantime.
And of course don't expect results right away. Trends have a habit of continuing,
so the silver miners could easily have another crappy year. But at some point
both silver and its derivatives (including mining shares) will start moving
in the right direction. Listen to this interview with
Sprott Asset Management's Rick Rule for inspiration.