(Top) Comparison of the regular tax on wages only (not taking into account any deductions) in 2000 and 2004 (orange and blue lines respectively) with the tentative minimum tax (AMT before deducting regular tax) (same brown line for both 2000 and 2004) for a married couple who are filing jointly. Two dashed lines show the margins between the tentative minimum tax and the regular tax rates in 2000 and 2004—and how this margin was becoming narrower from year to year. This means that not many deductions are needed before the AMT must be paid. And one needs to claim fewer deductions in subsequent years in order for the parity to be reached, and thus to get into the AMT territory. (The tentative minimum tax is the minimum amount of tax a person will end up paying. If it is less than the usual tax then there is no AMT.)
(Bottom) The same narrowing gap between regular tax and tentative minimum tax is shown in terms of effective tax rates paid on various amounts of AGI in 2000 and 2004.
English: The above figure shows the AMT as a function of AGI and compares it to the tax on wages only without any deduction for a married couple filing jointly. This  chart was created with R: R code x <- seq(50,500,1) y <- x regionA <- x <= 58 regionB <- x > 58 & x <= 175 regionC <- x > 175 y[regionA] <- 0 y[regionB] <- (x[regionB] - 58) * 0.26 y[regionC] <- (175 - 58) * 0.26 + (x[regionC] - 175) * 0.28 # standard_deducation <- 9.7 # exemptions <- 2 # exemption_credit <- 3.1 baseline <- 0 region1 <- x <= baseline region2 <- x > baseline & x <= baseline + 14.3 region3 <- x > baseline + 7.15 & x <= baseline + 58.1 region4 <- x > baseline + 58.1 & x <= baseline + 117.25 region5 <- x > baseline + 117.25 & x <= baseline + 178.65 region6 <- x > baseline + 178.65 & x <= baseline + 319.1 region7 <- x > baseline + 317.1 x2 <- x y2 <- x y2[region1] <- 0 y2[region2] <- 0.1 * x2[region2] y2[region3] <- 1.43 + 0.15 * (x2[region3] - 14.3) y2[region4] <- 8 + 0.25 * (x2[region4] - 58.1) y2[region5] <- 22.7875 + 0.28 * (x2[region5] - 117.25) y2[region6] <- 39.9795 + 0.33 * (x2[region6] - 178.65) y2[region7] <- 86.328 + 0.35 * (x2[region7] - 319.1) # standard_deduction <- 7.35 # exemption_credit <- 2.8 baseline <- 0 region1 <- x <= baseline region2 <- x > baseline & x <= baseline + 43.85 region3 <- x > baseline + 43.85 & x <= baseline + 105.95 region4 <- x > baseline + 105.95 & x <= baseline + 161.45 region5 <- x > baseline + 161.45 & x <= baseline + 288.35 region6 <- x > baseline + 288.35 pass1 <- 43.85 * 0.15 pass2 <- pass1 + (105.95 - 43.85) * 0.28 pass3 <- pass2 + (161.45 - 105.95) * 0.31 pass4 <- pass3 + (288.35 - 161.45) * 0.36 #x3 <- x-baseline x3 <- x y3 <- x y3[region1] <- 0 y3[region2] <- 0.15 * x3[region2] y3[region3] <- pass1 + 0.28 * (x3[region3] - 43.85) y3[region4] <- pass2 + 0.31 * (x3[region4] - 105.95) y3[region5] <- pass3 + 0.36 * (x3[region5] - 161.45) y3[region6] <- pass4 + 0.396 * (x3[region6] - 288.35) #setwd("~/") bitmap(file="AMT.png",type="png256",width=6,height=6,res=300,pointsize=12) par(mfrow=c(2,1)) par(mar=c(3.5,3.5,1,3.5)) par(xaxs="i") par(yaxs="i") par(mgp=c(2,0.5,0)) par(xaxt="n") plot(range(x),range(c(y,y2,y3)),type="n",xlab="Adjusted Gross Income (thousands)",ylab="Tax (thousands)",log="x") par(xaxt="s") axis(1,at=c(20,50,100,200,500)) mtext("Adjusted Gross Income (thousands)",1,2) lines(x,y,lwd=3) lines(x,y2,col="blue",lwd=3) lines(x,(y2-y),col="blue",lty=2,lwd=3) lines(x,y3,col="orange",lwd=3) lines(x,(y3-y),col="orange",lty=2,lwd=3) legend("topleft",legend=c("2004 tax","2000 tax","TMT","2004 tax minus TMT","2000 tax minus TMT"),col=c("blue","orange","black","blue","orange"),lty=c(1,1,1,2,2),lwd=2,bty="n") par(mar=c(3.5,3.5,1,3.5)) par(xaxs="i") par(yaxs="i") par(mgp=c(2,0.5,0)) par(xaxt="n") plot(range(x),100*range(c(y/x,y2/x,y3/x)),type="n",xlab="Adjusted Gross Income (thousands)",ylab="% Tax rate",log="x") par(xaxt="s") axis(1,at=c(20,50,100,200,500)) mtext("Adjusted Gross Income (thousands)",1,2) lines(x,100*y/x,lwd=3) lines(x,100*y2/x,col="blue",lwd=3) lines(x,100*y3/x,col="orange",lwd=3) legend("topleft",legend=c("2004 tax","2000 tax","TMT"),col=c("blue","orange","black"),lty=c(1,1,1,2,2),lwd=2,bty="n") dev.off() Data sources: calculation scheme, sect"Calculating the AMT"[1] 2004 marginal tax rates [2] 2000 marginal tax rates [3]