&gt; Pray tell how does one measure demand elasticity[0]?<p>The phrase &quot;during CPI calculation&quot; should be the key to understanding here. CPI tells you how much prices have gone up or down <i>generally</i>, by just sending a bunch of secret-shoppers around to measure a bunch of prices.<p>Knowing the treasury&#x27;s current bond interest rates, the current exchange rate, and Core CPI, you can derive economy-wide aggregate demand—which is the point of the whole exercise. You can then look at any given good&#x27;s economy-wide demand (i.e. the same formula, where Core CPI is calculated in terms of just that one good) relative to total demand as a time series, take their co-variance, and that&#x27;s the good&#x27;s demand-elasticity. (All the numbers are public at every step; there&#x27;s no real way to fudge them.)<p>&gt; Would tampons be covered by UBFS? Let&#x27;s say then we allow for UBFS to cover female menstrual products. Would cups then be covered? Why or why not?<p>Again: you plug in the demand-elasticity formula and get an answer. No politics, just cold automated logic. Female menstrual products <i>as a category</i> are very likely to be calculated to be inelastic.<p>Now, how that breaks down to individual items <i>within</i> the category is something I didn&#x27;t define. As a raw guess, the government could define base inelastic-value for the category, which would apply as a sort of rebate to all the items in that category. Any individual item&#x27;s price <i>should</i>, after this &quot;rebate&quot;, reflect exactly and only its additional elastic demand—making the &quot;premium&quot; products cost some number of nicety-dollars, while the &quot;economy&quot; products in that class cost &quot;nothing&quot; in nicety-dollar terms. (The real key there is the creation of a law preventing companies from increasing their prices in response to this—because, without market manipulation, of course prices would rise to reflect all the same competitive demand as before, <i>plus</i> the extra &quot;free&quot; votes each person got. The law would just need to force companies receiving necessity-dollars to price according to demand in an alternate world where demand was exactly [the amount of inelastic-demand] lower.)<p>&gt; one word: Arbitrage.<p>No reason to allow individuals to trade in necessities at all, which would nearly completely prevent arbitraging opportunities. (e.g. it&#x27;s obvious enough that you shouldn&#x27;t be able to rent your necessity-dollar-paid apartment out on AirBnB.) Consider anything paid for in necessity-dollars to be tainted and have no legal nicety-dollar value after that.