I've read similar posts before, but not during a time when I was actually making Roth conversions, so I've never dug into the reasoning as to why it's better to convert when the market is down.
Could you (or anyone) explain, or point me to a primer, as to why down markets are a good time to convert to Roth?
Suppose you have 1000 shares of a fund or stock valued at $100/share in your tIRA. $100K total.
And suppose you have room to convert $50K worth this year. If you convert today, you convert 500 shares, and you now have 500 shares in your tIRA and 500 shares in your Roth. $50K in each account.
But what if instead the per share price drops to $90/share, a 10% drop. If you convert $50K while it's down, you can convert 50,000/90, or 555 shares. Now you have 445 shares in the tIRA and 555 in the Roth. If the price goes back up to $100/share, you have $44,500 in your tIRA and $55,500 in your Roth.
I'm assuming taxes are taken from an outside account, but the taxable income is $50,000 in either case so this is static. You can take the tax out of the conversion and the effect is basically the same.
So by doing conversion at a low point, you got more wound up with $5,500 "free" conversion, assuming the price recovered.
Conversely, if you convert at a high, you get fewer shares converted.
Of course you never know when prices will be at a low or high. Since on average prices will be higher at the end of the year than at the beginning, you might want to convert early in the year. But you could do a little bit of market timing by choosing when to convert.
I don't have stocks in my tIRA anyway so I don't see much fluctuation. I convert when I know I can safely early in the year, and top it off to hit whatever MAGI or taxable income target I have very late in the year when I know what the rest of my income for the year is.