Archive
How to Calculate USDi’s Current Value
I haven’t been writing a lot during August, nor have I done many podcast episodes. I feel like I make this apology almost every year, but it seems every year August just gets slower, and slower, and slower – and any content I push out gets less engagement during August than during any other full month (although the end of December, naturally, gets very thin as well. It’s really remarkable how August has changed during my career. In the 1990s, there were maybe a couple of weeks that were a little thin in the markets, but that has metastasized so that now it’s all of August and a week or two into July. I am speaking of the US markets – Europe has always been slow for the second half of the summer, at least in my experience, and I don’t know if there has been much change in that over the last few decades.
In any event, I’m more than happy as a writer to take a little time off and recharge. As an entrepreneur? Not so much.
This is, though, a good time for a ‘utility’ post. As readers know, a few months ago we launched USDi, the first CPI-linked cryptocurrency that’s fully backed by traditional finance assets. Because those assets for the most part reside in a private fund (which, because it’s a private fund issued under Reg D, I can’t talk much about on a public post so forgive my vagueness here about what the fund does and how), there is regularly confusion when potential buyers of USDi think that they are buying a share of the fund. They are not, for two reasons. The first is that a coin that represents a tokenized share of a traditional-finance fund would clearly be a security under US law, which creates lots of other complexities that we don’t want: for example just as I can’t tell you much about the fund, if the token was a security then I couldn’t tell you much about that, either! Which would make distribution difficult, to say the least.
The second reason that we didn’t want the coin to represent a tokenized share of the fund is that then the coin would not exactly track CPI. It is important that the coin be a zero-risk instrument, and I illustrate why that’s important in the post “USELESS Coin vs Very Useful Coin”. Accordingly, USDi’s value is entirely formulaic, and known in advance by at least a few weeks. It’s my purpose today to explain how the value of USDi is derived from CPI prints.
USDi, like TIPS and US CPI swaps, is linked to the Non-seasonally Adjusted Consumer Price Index for All Urban Consumers…the NSA CPI for short. The CPI that is released every month is related to this number – specifically, the ‘headline CPI’ is the month-on-month percentage change in the Seasonally-adjusted number. Here is where you find that number (rounded, of course) in the monthly BLS release found at https://www.bls.gov/news.release/cpi.nr0.htm:
The problem with using a seasonally-adjusted number is, you guessed it, that the seasonal adjustment factors can change. Consequently, all inflation derivatives rely on NSA numbers, which are almost never revised. In the same report linked above, the BLS notes the NSA number:
The highlighted number, 323.048 in this case, is the number that TIPS traders and inflation swaps traders care about. And, if you buy USDi, you will care about this number as well. This is the price index value defined relative to the base of 100.000 representing the average of the 1982-1984 price level. The index value of 323.048 tells you that the (quality-adjusted) price level has risen 223.048% since the early 1980s, slightly more than a tripling!
(As an aside, the BLS has an enormous number of NSA series for different subcomponents available. You can see and chart a lot of them here: https://data.bls.gov/dataQuery/find?fq=survey:%5Bcu%5D&s=popularity:D )
Now, the BLS reports this number just once a month, and in arrears. It was mid-August when they reported the July CPI referenced above. So we have two things we need to account for when we turn this into an index that USDi (or TIPS or inflation swaps) can track: 1. We have a monthly number, and we need a daily number – or in USDi’s case, one number every block, and 2. We have numbers for every month ending in July, but today isn’t July, so we need something for today. Let’s call the index value that we are going to construct, to use for TIPS/swaps/USDi, the “Reference CPI.”[1]
The second problem is handled in the simplest way possible: we just lag the data.[2]
So when we got the July data this month, we have the Ref CPI for October 1 (the 323.048 number I mentioned above). We already have the Ref CPI for September 1 (that was the June CPI, reported in July, 322.561). So now, we can straight-line interpolate the Ref CPI for any day in between those two dates, based on the number of calendar days in that month. So, the Ref CPI for September 2nd is:
1/30 * 323.048 + 29/30 * 322.561 = 322.57723
Voila, that’s just what the Treasury calculates for September 2nd, which isn’t surprising because that’s how math works.
Now, the only subtlety to USDi is that while TIPS and CPI swaps have one settlement per day USDi in principle is tradeable 24/7. That means that if we changed the Ref CPI for USDi just once per day, at 1 second before midnight every day you could buy USDi and then sell it at 1 second after midnight and get the entire day’s interest. That doesn’t seem fair. The blockchain is much closer to continuous settlement, so we have to interpolate not by day, but by block. On Ethereum (where USDi exists, initially), a block is roughly 10-15 seconds long, so USDi accrues interest basically every 10 seconds. The actual code for USDi looks at the block number and does the exact same calculation that we do above except that it is interpolating between the first block in September and the first block in October. You can get very close to the right answer by simply using spreadsheet NOW() functions, which in Google Sheets has 1-second precision. I do the approximate calculation for USDi on a Google Sheet here: https://docs.google.com/spreadsheets/d/1UnPzAu-U2zy5TEIcxgLBqkVP7QNtBJhwrwLnHt9EitM/edit?gid=0#gid=0
Let’s see, why did I want to calculate the Reference CPI? Oh, I remember: I want to find the price of USDi for a given time, in the past or present or any time up until (for now) the end of September. We have done all of the work except for the last step, which is to divide the current price level index – the Reference CPI – by the base price level index. For USDi, we defined the denominator as the December 2024 CPI. This is why we say that USDi is a dollar that preserves the purchasing power of a December 2024 dollar.
The December 2024 CPI was 315.605. Since the December 2024 CPI was also the Reference CPI for March 1st (see the handy drawing above), that means the value of USDi on March 1st was (drum roll) 315.605/315.605 = 1.000000. The value of USDi on October 1st will be 323.048/315.605 = $1.023583.
So the USDi coin is not a fund, nor a share of a fund. It is a time machine.
[1] The Reference CPI for TIPS and swaps is identical. The Treasury calculates them too, and reports them at https://treasurydirect.gov/auctions/announcements-data-results/tips-cpi-data/ (look for the PDF and XML files for the “Reference CPI Numbers and Daily Index Ratios Table.”)
[2] In principle, we could take the recent data trend and project to the current date, which would make it contemporaneous but lose accuracy…since when the inflation data is actually released, we will find out that method isn’t perfect. It would also be confusing, since on any given day in the past there would now be the actual CPI data and the previously-used projected-trend data. Since the importance of the exact timing of the price level diminishes with distance, while the two-index confusion would persist, the simple-lag method makes sense to me.
Inflation Guy’s CPI Summary (July 2025)
The inflation story and the employment story are about the only things rippling the still summer waters these days, it seems. The weak employment data in the most-recent report got equity investors very excited since every analyst worth his or her salt believes that lower rates are good for the companies he/she covers, but those companies will surely be able to avoid losing business in an economic slowdown. And, to be fair, because the goods and services sectors in the US (and global) economy are out-of-sync, any recession is likely to be fairly shallow (and being out-of-sync is probably why the recession has been so delayed – different sectors are having recessions at different times. I discussed this in last week’s podcast, Ep. 147: Out of Sync).
But the fly in the ointment would be if inflation heads higher, wouldn’t it?
Well, maybe not so much. In normal times, probably. But in today’s world there is a nice, built-in excuse for any inflation uptick: it’s the tariff effect! It is amazing how focused on tariffs everybody has been, when they forecast/analyze the CPI report. The core goods sector of the economy is about one-fifth of total consumption. Tariffs will (and finally are) driving this higher, but that story will eventually pass. Core goods will not be what keeps inflation high or sends it higher in 2026. But you know why everyone wants to focus on it? Because if you can blame the inflation uptick on tariffs, then you can argue that rate cuts still make sense. More on that later, but when you look at the monthly changes in real yields and inflation expectations you can see what is happening: yields are down, inflation expectations basically unchanged, over the last month. The best of all worlds!
Which brings us to today’s report. The consensus expectations were for +0.23% on headline CPI (seasonally-adjusted), +0.29% on core, pushing the y/y figures higher for both of them as we drop off soft data from last summer. The actual prints were +0.197% on headline (yay!) and +0.322% on core (boo!). That was the highest m/m core inflation figure since January, and the first time since then that core has been higher than consensus expectations. It also was the highest m/m core number, other than January’s tariff-related spike, since March 2024.
The category breakdown was interesting for a change because the top culprits were Medical Care, Recreation, and Other.
To be fair, housing would have contributed more except for another drop in Lodging Away from Home. Seasonally-adjusted prices for lodging away from home have now fallen 7.3% since January. I have been working on the assumption that this is a deportations story, or possibly a tourism story (I don’t really think ‘foreigners aren’t visiting the US because they hate Trump’ is really happening but in some quarters that’s the story they’re selling). But if you look at this chart and notice the times that hotel prices declined meaningfully, there’s an argument that it’s a recession story. Or that it could be, if it continues to slide.
Primary rents accelerated slightly m/m, +0.26% vs 0.23% last month, but Owners’ Equivalent Rent decelerated to +0.28% vs 0.30%. Both are playing to form, but it’s worth keeping an eye on Primary Rents here. Deportations as an inflation story would show up in Lodging Away from Home but it also could show up eventually in rents – but a recession wouldn’t be expected have any meaningful impact on rents. So how those two series behave might give us a clue. Or maybe not; perhaps I’m trying to read too much into this.
Core goods accelerated again. The bounce was totally expected, but now that we are over +1% (+1.17% y/y) we are clearly seeing some of the impact of tariffs. Core services is more interesting, though. Even with rents decelerating and Lodging Away from Home dropping again, Core services ticked higher.
Indeed, lumping core services and core goods together, but taking out shelter, and we can see that the underlying core dynamic looks like it had been bottoming anyway and might be heading higher.
A large jump in airfares (+4.04% m/m) is partly to blame this month…but in March airfares were -5.3% m/m and the worst since 2021 while today’s number was the highest since 2022. Since COVID, airfares have just been really unstable, or the seasonals have been unstable, or both. I am not worrying too much about this jump.
Airline fares are 0.9% of CPI, but this volatility has added to the overall volatility of the CPI. And before you say ‘this is a consequence of resource constraints at the BLS!’ you should realize that airfares are not collected by people with clipboards but by web scrapers. However this is yet another reminder that Median CPI is a better way to look the overall trend, so as not to be distracted by little categories. My early guess at Median this month is +0.276%, a bit better than last month. But there is nothing here that looks to me like a moderating trend to lower inflation.
In fact, median y/y ought to tick higher again this month to about 3.65%. It is stabilizing in the high-3s. The next few monthly figures to drop off will be 0.3s, so I don’t think we will see median y/y head back to the 4% level. But having said that, there is one development that bears watching.
Core services less rent-of-shelter, aka “Supercore”, rose +0.48% m/m. If higher tariffs and deportations lead to more domestic employment and higher wages – which they should, but it isn’t yet really in the data as employment looked weak and the Wage Growth Tracker ticked down to +4.1% y/y this month – then this part is what will keep inflation uncomfortably high even if rents continue to decline (I don’t see them declining lots further than this) and goods inflation eventually declines after the tariff effect passes through. That isn’t today’s story. But it might be a 2026 story. Stay tuned. At the tails of the distribution this month we had greater than -10% annualized monthly inflation from three non-core categories while greater than +10% from eight non-core categories – including motor vehicle parts and equipment and miscellaneous personal goods, which are tariff stories, but also tenants and household insurance, miscellaneous personal services, public transportation, and motor vehicle maintenance and repair. Those are all service stories. As is this one, although it’s also a goods story indirectly (I explain further in the Q3 Quarterly Inflation Outlook, due out tomorrow – subscribe at https://inflationguy.blog/shop).
Overall, the underlying trend is the same: we’re settling in the high-3s for median inflation. Last month, I said that unless the economy starts to soften more seriously there just isn’t a good argument right now for rate cuts and the optics of rising year/year inflation would make it more challenging for the FOMC to consider an ease. That is still true. If Fed credibility matters to inflation, then inflation should start heading up because we are clearly getting more doves. If tariffs matter, inflation should be heading up because the tariffs are now showing and will be an effect for a while. If money growth matters, inflation should be heading up because M2 growth is back to +4.5% and accelerating.
But the core question is whether the Fed cares about inflation right now. Listening to their public statements, it doesn’t appear they do. One might argue that they are just supremely confident that if the Unemployment Rate heads higher, inflation will head lower so they have some room to move. To be honest, “supremely confident” and “Fed official” are not phrases that should appear in the same paragraph except sardonically. Nevertheless, the Fed is likely to ease soon, and likely multiple times before the end of the year.
And they’re worried that President Trump is going to hurt Fed credibility! That’s a little like the streetwalker who is afraid that this skirt is going to make her look cheap. Honey, that ship has sailed.
One final announcement. If you’re an investor in cryptocurrencies (in particular, stable coins) and have a Telegram account, consider joining the read-only USDi_Coin room https://t.me/USDi_Coin where the USDi Coin price is updated every four hours or so…and where many of these charts are also posted shortly after CPI just as I used to do on Twitter.
