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Lafleur","avatar_url":"https://avatars-next.observableusercontent.com/b09275e7b6b3576ac1a1f4c68e1b8ce25afb4b108c78fab2bdadfe497f992b62","tier":null,"bio":"","followed_by_you":false,"follows_you":false}],"members":[{"type":"team","id":"217b00e487e758d3","login":"etienne-pema-lafleur","name":"Etienne Pema Lafleur","avatar_url":"https://avatars-next.observableusercontent.com/b09275e7b6b3576ac1a1f4c68e1b8ce25afb4b108c78fab2bdadfe497f992b62","tier":"starter_2024","role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":null,"type":"notebook","body":{"titling":"auto","title":"Mortgage Luck: The $1,000/Month Timing Tax","cells":[{"id":1,"value":"# Mortgage Luck: The $1,000/Month Timing Tax\n\nYou and your neighbor bought the same house. They got 2.7%. You got 6.9%. Here’s exactly what that cost you.\n\nDrag the slider to change the week you locked your rate. The house, the down payment, and your credit stay the same. Only the timing changes.","pinned":false,"hidden":false,"mode":"md","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":2,"value":"const loanAmt = view(Inputs.number({ label: \"Loan amount ($)\", value: 400_000, step: 10_000, min: 50_000, max: 2_000_000 }))","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":3,"value":"const closeIdx = view((() => {\n const input = Inputs.range([0, data.length - 1], {\n label: \"Your close date\",\n value: data.length - 1,\n step: 1\n });\n // The raw position in the data means nothing to a reader; the date appears in the stats below.\n input.querySelector(\"input[type=number]\").style.display = \"none\";\n return input;\n})())","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":4,"value":"html`

${usd(payment)}

/ month

${usd(interest)}

total interest over 30 yrs

${selected.rate.toFixed(2)}%

rate on ${fmtDate(selected.date)}

`","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":5,"value":"Plot.plot({\n width,\n height: 300,\n x: { label: \"Date\" },\n y: { label: \"30-yr Fixed Rate (%)\", grid: true },\n marks: [\n Plot.lineY(data, { x: \"date\", y: \"rate\", stroke: \"#4a90d9\", strokeWidth: 1.5 }),\n Plot.ruleX([selected.date], { stroke: \"red\", strokeWidth: 2 }),\n Plot.dot([selected], { x: \"date\", y: \"rate\", fill: \"red\", r: 5 })\n ]\n})","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":6,"value":"{\n const low = d3.least(data, d => d.rate);\n const high = d3.greatest(data, d => d.rate);\n const lowPay = monthlyPayment(loanAmt, low.rate);\n const highPay = monthlyPayment(loanAmt, high.rate);\n display(md`**Best vs. worst week since 2015, on a ${usd(loanAmt)} loan:** ${low.rate.toFixed(2)}% on ${fmtDate(low.date)} costs ${usd(lowPay)} a month. ${high.rate.toFixed(2)}% on ${fmtDate(high.date)} costs ${usd(highPay)} a month. That is **${usd(highPay - lowPay)} a month**, or **${usd((highPay - lowPay) * 360)}** in extra interest if the loan runs its full 30 years with no refinance.\n\nPrincipal and interest only. Rates are the national weekly average from Freddie Mac's survey, so an individual borrower's rate will differ.\n\nData: © Freddie Mac, via FRED (series MORTGAGE30US), weekly, Jan 2015 to ${fmtDate(data[data.length - 1].date)}. Stored in this notebook because FRED blocks direct browser requests from Observable.`);\n}","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":7,"value":"function monthlyPayment(principal, annualRate) {\n const r = annualRate / 100 / 12; // monthly rate as decimal\n const n = 360; // 30 years × 12\n if (r === 0) return principal / n;\n return principal * (r * (1 + r) ** n) / ((1 + r) ** n - 1);\n}","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":8,"value":"const selected = data[Math.round(closeIdx)]","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":9,"value":"const payment = monthlyPayment(loanAmt, selected.rate)","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":10,"value":"const lifetime = payment * 360","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":11,"value":"const interest = lifetime - loanAmt","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":12,"value":"const usd = d3.format(\"$,.0f\")","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":13,"value":"const fmtDate = d => d.toLocaleDateString(\"en-US\", { year: \"numeric\", month: \"short\", day: \"numeric\", timeZone: \"UTC\" })","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"},{"id":14,"value":"$3c","pinned":false,"hidden":false,"mode":"ts","author":"$undefined","summary":"$undefined","tool":"$undefined","providerMetadata":"$undefined","attachments":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W3d","stdlib":"2"}} 33:null