From d50af1161e365a5b83270899933b240ab61bd7b7 Mon Sep 17 00:00:00 2001
From: RunasSudo <runassudo@yingtongli.me>
Date: Mon, 7 Jun 2021 20:52:18 +1000
Subject: [PATCH] Implement --quota-mode ers97

---
 html/index.html             |   8 +-
 html/index.js               |  30 ++++++-
 html/worker.js              |   6 +-
 src/election.rs             |   6 +-
 src/main.rs                 |  10 ++-
 src/numbers/fixed.rs        |   4 +-
 src/numbers/native.rs       |   4 +-
 src/numbers/rational_num.rs |   4 +-
 src/numbers/rational_rug.rs |   4 +-
 src/stv/mod.rs              | 169 +++++++++++++++++++++++++++++-------
 src/stv/wasm.rs             |  16 ++--
 tests/aec.rs                |   1 +
 tests/prsa.rs               |   1 +
 13 files changed, 203 insertions(+), 60 deletions(-)

diff --git a/html/index.html b/html/index.html
index 019d98b..1680b3e 100644
--- a/html/index.html
+++ b/html/index.html
@@ -40,7 +40,7 @@
 						<!--<option value="meek">Meek STV</option>
 						<option value="wright">Wright STV</option>-->
 						<option value="prsa77">PRSA 1977</option>
-						<!--<option value="ers97">ERS97</option>-->
+						<option value="ers97">ERS97</option>
 					</select>
 				</label>
 				<button id="btnAdvancedOptions" onclick="clickAdvancedOptions()">Show advanced options</button>
@@ -70,13 +70,13 @@
 								<option value="hare_exact">Hare (exact)</option>
 							</select>
 						</label>
-						<!--<label>
+						<label>
 							<select id="selQuotaMode">
 								<option value="static" selected>Static quota</option>
-								<option value="progressive">Progressive quota</option>
+								<!--<option value="progressive">Progressive quota</option>-->
 								<option value="ers97">Static with ERS97 rules</option>
 							</select>
-						</label>-->
+						</label>
 					</div>
 					<div>
 						<label>
diff --git a/html/index.js b/html/index.js
index 78bc267..cf9f326 100644
--- a/html/index.js
+++ b/html/index.js
@@ -97,6 +97,7 @@ async function clickCount() {
 		document.getElementById('chkRoundQuota').checked ? parseInt(document.getElementById('txtRoundQuota').value) : null,
 		document.getElementById('selQuota').value,
 		document.getElementById('selQuotaCriterion').value,
+		document.getElementById('selQuotaMode').value,
 		document.getElementById('selTransfers').value,
 		document.getElementById('selSurplus').value,
 		document.getElementById('selPapers').value == 'transferable',
@@ -291,7 +292,7 @@ function changePreset() {
 	if (document.getElementById('selPreset').value === 'scottish') {
 		document.getElementById('selQuotaCriterion').value = 'geq';
 		document.getElementById('selQuota').value = 'droop';
-		//document.getElementById('selQuotaMode').value = 'static';
+		document.getElementById('selQuotaMode').value = 'static';
 		//document.getElementById('chkBulkElection').checked = true;
 		//document.getElementById('chkBulkExclusion').checked = false;
 		//document.getElementById('chkDeferSurpluses').checked = false;
@@ -311,7 +312,7 @@ function changePreset() {
 	} else if (document.getElementById('selPreset').value === 'senate') {
 		document.getElementById('selQuotaCriterion').value = 'geq';
 		document.getElementById('selQuota').value = 'droop';
-		//document.getElementById('selQuotaMode').value = 'static';
+		document.getElementById('selQuotaMode').value = 'static';
 		//document.getElementById('chkBulkElection').checked = true;
 		//document.getElementById('chkBulkExclusion').checked = true;
 		//document.getElementById('chkDeferSurpluses').checked = false;
@@ -332,7 +333,7 @@ function changePreset() {
 	} else if (document.getElementById('selPreset').value === 'prsa77') {
 		document.getElementById('selQuotaCriterion').value = 'geq';
 		document.getElementById('selQuota').value = 'droop';
-		//document.getElementById('selQuotaMode').value = 'static';
+		document.getElementById('selQuotaMode').value = 'static';
 		//document.getElementById('chkBulkElection').checked = true;
 		//document.getElementById('chkBulkExclusion').checked = false;
 		//document.getElementById('chkDeferSurpluses').checked = true;
@@ -352,5 +353,28 @@ function changePreset() {
 		document.getElementById('selPapers').value = 'transferable';
 		document.getElementById('selExclusion').value = 'parcels_by_order';
 		//document.getElementById('selTies').value = 'backwards_random';
+	} else if (document.getElementById('selPreset').value === 'ers97') {
+		document.getElementById('selQuotaCriterion').value = 'geq';
+		document.getElementById('selQuota').value = 'droop_exact';
+		document.getElementById('selQuotaMode').value = 'ers97';
+		//document.getElementById('chkBulkElection').checked = true;
+		//document.getElementById('chkBulkExclusion').checked = true;
+		//document.getElementById('chkDeferSurpluses').checked = true;
+		document.getElementById('selNumbers').value = 'fixed';
+		document.getElementById('txtDP').value = '5';
+		document.getElementById('txtPPDP').value = '2';
+		document.getElementById('chkRoundQuota').checked = true;
+		document.getElementById('txtRoundQuota').value = '2';
+		document.getElementById('chkRoundVotes').checked = true;
+		document.getElementById('txtRoundVotes').value = '2';
+		document.getElementById('chkRoundTVs').checked = true;
+		document.getElementById('txtRoundTVs').value = '2';
+		document.getElementById('chkRoundWeights').checked = true;
+		document.getElementById('txtRoundWeights').value = '2';
+		document.getElementById('selSurplus').value = 'by_size';
+		document.getElementById('selTransfers').value = 'eg';
+		document.getElementById('selPapers').value = 'transferable';
+		document.getElementById('selExclusion').value = 'by_value';
+		//document.getElementById('selTies').value = 'forwards_random';
 	}
 }
diff --git a/html/worker.js b/html/worker.js
index c549fe3..d25b23d 100644
--- a/html/worker.js
+++ b/html/worker.js
@@ -25,15 +25,15 @@ onmessage = function(evt) {
 		// Init election
 		let election = wasm['election_from_blt_' + numbers](evt.data.electionData);
 		
-		// Init results table
-		postMessage({'type': 'initResultsTable', 'content': wasm['init_results_table_' + numbers](election)});
-		
 		// Init STV options
 		let opts = wasm.STVOptions.new.apply(null, evt.data.optsStr);
 		
 		// Describe count
 		postMessage({'type': 'describeCount', 'content': wasm['describe_count_' + numbers](evt.data.filePath, election, opts)});
 		
+		// Init results table
+		postMessage({'type': 'initResultsTable', 'content': wasm['init_results_table_' + numbers](election, opts)});
+		
 		// Step election
 		let state = wasm['CountState' + numbers].new(election);
 		wasm['count_init_' + numbers](state, opts);
diff --git a/src/election.rs b/src/election.rs
index 602513c..4a06dd9 100644
--- a/src/election.rs
+++ b/src/election.rs
@@ -102,7 +102,8 @@ pub struct CountState<'a, N> {
 	pub exhausted: CountCard<'a, N>,
 	pub loss_fraction: CountCard<'a, N>,
 	
-	pub quota: N,
+	pub quota: Option<N>,
+	pub vote_required_election: Option<N>,
 	
 	pub num_elected: usize,
 	pub num_excluded: usize,
@@ -119,7 +120,8 @@ impl<'a, N: Number> CountState<'a, N> {
 			candidates: HashMap::new(),
 			exhausted: CountCard::new(),
 			loss_fraction: CountCard::new(),
-			quota: N::new(),
+			quota: None,
+			vote_required_election: None,
 			num_elected: 0,
 			num_excluded: 0,
 			kind: None,
diff --git a/src/main.rs b/src/main.rs
index ec44b7c..2447bf5 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -89,6 +89,10 @@ struct STV {
 	#[clap(help_heading=Some("QUOTA"), short='c', long, possible_values=&["geq", "gt"], default_value="gt", value_name="criterion")]
 	quota_criterion: String,
 	
+	// Whether to apply a form of progressive quota
+	#[clap(help_heading=Some("QUOTA"), long, possible_values=&["static", "ers97"], default_value="static", value_name="mode")]
+	quota_mode: String,
+	
 	// ------------------
 	// -- STV variants --
 	
@@ -160,6 +164,7 @@ where
 		cmd_opts.round_quota,
 		&cmd_opts.quota,
 		&cmd_opts.quota_criterion,
+		&cmd_opts.quota_mode,
 		&cmd_opts.surplus,
 		&cmd_opts.surplus_order,
 		cmd_opts.transferable_only,
@@ -249,7 +254,10 @@ fn print_stage<N: Number>(stage_num: usize, result: &StageResult<N>, cmd_opts: &
 	total_vote += &state.loss_fraction.votes;
 	println!("Total votes: {:.dps$}", total_vote, dps=cmd_opts.pp_decimals);
 	
-	println!("Quota: {:.dps$}", state.quota, dps=cmd_opts.pp_decimals);
+	println!("Quota: {:.dps$}", state.quota.as_ref().unwrap(), dps=cmd_opts.pp_decimals);
+	if cmd_opts.quota_mode == "ers97" {
+		println!("Vote required for election: {:.dps$}", state.vote_required_election.as_ref().unwrap(), dps=cmd_opts.pp_decimals);
+	}
 	
 	println!("");
 }
diff --git a/src/numbers/fixed.rs b/src/numbers/fixed.rs
index d9f3e30..968004d 100644
--- a/src/numbers/fixed.rs
+++ b/src/numbers/fixed.rs
@@ -192,9 +192,7 @@ impl ops::Add<&Self> for Fixed {
 
 impl ops::Sub<&Self> for Fixed {
 	type Output = Self;
-	fn sub(self, _rhs: &Self) -> Self::Output {
-		todo!()
-	}
+	fn sub(self, rhs: &Self) -> Self::Output { Self(self.0 - &rhs.0) }
 }
 
 impl ops::Mul<&Self> for Fixed {
diff --git a/src/numbers/native.rs b/src/numbers/native.rs
index 5443e43..534b6b0 100644
--- a/src/numbers/native.rs
+++ b/src/numbers/native.rs
@@ -136,9 +136,7 @@ impl ops::Add<&NativeFloat64> for NativeFloat64 {
 
 impl ops::Sub<&NativeFloat64> for NativeFloat64 {
 	type Output = NativeFloat64;
-	fn sub(self, _rhs: &NativeFloat64) -> Self::Output {
-		todo!()
-	}
+	fn sub(self, rhs: &NativeFloat64) -> Self::Output { Self(self.0 - &rhs.0) }
 }
 
 impl ops::Mul<&NativeFloat64> for NativeFloat64 {
diff --git a/src/numbers/rational_num.rs b/src/numbers/rational_num.rs
index c94a1d3..2643269 100644
--- a/src/numbers/rational_num.rs
+++ b/src/numbers/rational_num.rs
@@ -183,9 +183,7 @@ impl ops::Add<&Rational> for Rational {
 
 impl ops::Sub<&Rational> for Rational {
 	type Output = Rational;
-	fn sub(self, _rhs: &Rational) -> Self::Output {
-		todo!()
-	}
+	fn sub(self, rhs: &Rational) -> Self::Output { Self(self.0 - &rhs.0) }
 }
 
 impl ops::Mul<&Rational> for Rational {
diff --git a/src/numbers/rational_rug.rs b/src/numbers/rational_rug.rs
index 950aba4..8e92944 100644
--- a/src/numbers/rational_rug.rs
+++ b/src/numbers/rational_rug.rs
@@ -181,9 +181,7 @@ impl ops::Add<&Self> for Rational {
 
 impl ops::Sub<&Self> for Rational {
 	type Output = Self;
-	fn sub(self, _rhs: &Self) -> Self::Output {
-		todo!()
-	}
+	fn sub(self, rhs: &Self) -> Self::Output { Self(self.0 - &rhs.0) }
 }
 
 impl ops::Mul<&Self> for Rational {
diff --git a/src/stv/mod.rs b/src/stv/mod.rs
index 987d11c..ed5a5ce 100644
--- a/src/stv/mod.rs
+++ b/src/stv/mod.rs
@@ -37,6 +37,7 @@ pub struct STVOptions {
 	pub round_quota: Option<usize>,
 	pub quota: QuotaType,
 	pub quota_criterion: QuotaCriterion,
+	pub quota_mode: QuotaMode,
 	pub surplus: SurplusMethod,
 	pub surplus_order: SurplusOrder,
 	pub transferable_only: bool,
@@ -53,6 +54,7 @@ impl STVOptions {
 		round_quota: Option<usize>,
 		quota: &str,
 		quota_criterion: &str,
+		quota_mode: &str,
 		surplus: &str,
 		surplus_order: &str,
 		transferable_only: bool,
@@ -76,6 +78,11 @@ impl STVOptions {
 				"gt" => QuotaCriterion::Greater,
 				_ => panic!("Invalid --quota-criterion"),
 			},
+			quota_mode: match quota_mode {
+				"static" => QuotaMode::Static,
+				"ers97" => QuotaMode::ERS97,
+				_ => panic!("Invalid --quota-mode"),
+			},
 			surplus: match surplus {
 				"wig" => SurplusMethod::WIG,
 				"uig" => SurplusMethod::UIG,
@@ -111,6 +118,7 @@ impl STVOptions {
 		if let Some(dps) = self.round_quota { flags.push(format!("--round-quota {}", dps)); }
 		if self.quota != QuotaType::Droop { flags.push(self.quota.describe()); }
 		if self.quota_criterion != QuotaCriterion::GreaterOrEqual { flags.push(self.quota_criterion.describe()); }
+		if self.quota_mode != QuotaMode::Static { flags.push(self.quota_mode.describe()); }
 		if self.surplus != SurplusMethod::WIG { flags.push(self.surplus.describe()); }
 		if self.surplus_order != SurplusOrder::BySize { flags.push(self.surplus_order.describe()); }
 		if self.transferable_only { flags.push("--transferable-only".to_string()); }
@@ -158,6 +166,23 @@ impl QuotaCriterion {
 	}
 }
 
+#[wasm_bindgen]
+#[derive(Clone, Copy)]
+#[derive(PartialEq)]
+pub enum QuotaMode {
+	Static,
+	ERS97,
+}
+
+impl QuotaMode {
+	fn describe(self) -> String {
+		match self {
+			QuotaMode::Static => "--quota-mode static",
+			QuotaMode::ERS97 => "--quota-mode ers97",
+		}.to_string()
+	}
+}
+
 #[wasm_bindgen]
 #[derive(Clone, Copy)]
 #[derive(PartialEq)]
@@ -210,7 +235,7 @@ impl ExclusionMethod {
 		match self {
 			ExclusionMethod::SingleStage => "--exclusion single_stage",
 			ExclusionMethod::ByValue => "--exclusion by_value",
-			ExclusionMethod::ParcelsByOrder => "--exclusion parcels_by_value",
+			ExclusionMethod::ParcelsByOrder => "--exclusion parcels_by_order",
 		}.to_string()
 	}
 }
@@ -237,24 +262,26 @@ where
 	
 	// Continue exclusions
 	if continue_exclusion(&mut state, &opts) {
+		calculate_quota(&mut state, opts);
 		elect_meeting_quota(&mut state, opts);
 		return false;
 	}
 	
 	// Distribute surpluses
 	if distribute_surpluses(&mut state, &opts) {
+		calculate_quota(&mut state, opts);
 		elect_meeting_quota(&mut state, opts);
 		return false;
 	}
 	
 	// Attempt bulk election
 	if bulk_elect(&mut state) {
-		elect_meeting_quota(&mut state, opts);
 		return false;
 	}
 	
 	// Exclude lowest hopeful
 	if exclude_hopefuls(&mut state, &opts) {
+		calculate_quota(&mut state, opts);
 		elect_meeting_quota(&mut state, opts);
 		return false;
 	}
@@ -357,19 +384,13 @@ fn distribute_first_preferences<N: Number>(state: &mut CountState<N>) {
 	state.logger.log_literal("First preferences distributed.".to_string());
 }
 
-fn calculate_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
-	let mut log = String::new();
-	
-	// Calculate the total vote
-	state.quota = state.candidates.values().fold(N::zero(), |acc, cc| { acc + &cc.votes });
-	log.push_str(format!("{:.dps$} usable votes, so the quota is ", state.quota, dps=opts.pp_decimals).as_str());
-	
+fn total_to_quota<N: Number>(mut total: N, seats: usize, opts: &STVOptions) -> N {
 	match opts.quota {
 		QuotaType::Droop | QuotaType::DroopExact => {
-			state.quota /= N::from(state.election.seats + 1);
+			total /= N::from(seats + 1);
 		}
 		QuotaType::Hare | QuotaType::HareExact => {
-			state.quota /= N::from(state.election.seats);
+			total /= N::from(seats);
 		}
 	}
 	
@@ -379,25 +400,100 @@ fn calculate_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
 				// Increment to next available increment
 				let mut factor = N::from(10);
 				factor.pow_assign(dps as i32);
-				state.quota *= &factor;
-				state.quota.floor_mut(0);
-				state.quota += N::one();
-				state.quota /= factor;
+				total *= &factor;
+				total.floor_mut(0);
+				total += N::one();
+				total /= factor;
 			}
 			QuotaType::DroopExact | QuotaType::HareExact => {
 				// Round up to next available increment if necessary
-				let mut factor = N::from(10);
-				factor.pow_assign(dps as i32);
-				state.quota *= &factor;
-				state.quota.ceil_mut(0);
-				state.quota /= factor;
+				total.ceil_mut(dps);
 			}
 		}
 	}
 	
-	log.push_str(format!("{:.dps$}.", state.quota, dps=opts.pp_decimals).as_str());
+	return total;
+}
+
+fn calculate_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
+	// Calculate quota
+	if let None = state.quota {
+		let mut log = String::new();
+		
+		// Calculate the total vote
+		let total_vote = state.candidates.values().fold(N::zero(), |acc, cc| { acc + &cc.votes });
+		log.push_str(format!("{:.dps$} usable votes, so the quota is ", total_vote, dps=opts.pp_decimals).as_str());
+		
+		let quota = total_to_quota(total_vote, state.election.seats, opts);
+		
+		log.push_str(format!("{:.dps$}.", quota, dps=opts.pp_decimals).as_str());
+		state.quota = Some(quota);
+		state.logger.log_literal(log);
+	}
 	
-	state.logger.log_literal(log);
+	if let QuotaMode::ERS97 = opts.quota_mode {
+		// ERS97 rules
+		
+		// -------------------------
+		// Reduce quota if allowable
+		
+		if state.num_elected == 0 {
+			let mut log = String::new();
+			
+			// Calculate the total vote
+			let total_vote = state.candidates.values().fold(N::zero(), |acc, cc| { acc + &cc.votes });
+			log.push_str(format!("{:.dps$} usable votes, so the quota is reduced to ", total_vote, dps=opts.pp_decimals).as_str());
+			
+			let quota = total_to_quota(total_vote, state.election.seats, opts);
+			
+			if &quota < state.quota.as_ref().unwrap() {
+				log.push_str(format!("{:.dps$}.", quota, dps=opts.pp_decimals).as_str());
+				state.quota = Some(quota);
+				state.logger.log_literal(log);
+			}
+		}
+		
+		// ------------------------------------
+		// Calculate vote required for election
+		
+		if state.num_elected < state.election.seats {
+			let mut log = String::new();
+			
+			// Calculate total active vote
+			let total_active_vote = state.candidates.values().fold(N::zero(), |acc, cc| {
+				match cc.state {
+					CandidateState::ELECTED => { acc + &cc.votes - state.quota.as_ref().unwrap() }
+					_ => { acc + &cc.votes }
+				}
+			});
+			log.push_str(format!("Total active vote is {:.dps$}, so the vote required for election is ", total_active_vote, dps=opts.pp_decimals).as_str());
+			
+			let vote_req = total_to_quota(total_active_vote, state.election.seats - state.num_elected, opts);
+			
+			if &vote_req < state.quota.as_ref().unwrap() {
+				// VRE is less than the quota
+				if let Some(v) = &state.vote_required_election {
+					if &vote_req != v {
+						log.push_str(format!("{:.dps$}.", vote_req, dps=opts.pp_decimals).as_str());
+						state.vote_required_election = Some(vote_req);
+						state.logger.log_literal(log);
+					}
+				} else {
+					log.push_str(format!("{:.dps$}.", vote_req, dps=opts.pp_decimals).as_str());
+					state.vote_required_election = Some(vote_req);
+					state.logger.log_literal(log);
+				}
+			} else {
+				// VRE is not less than the quota, so use the quota
+				state.vote_required_election = state.quota.clone();
+			}
+		}
+	} else {
+		// No ERS97 rules
+		if let None = state.vote_required_election {
+			state.vote_required_election = state.quota.clone();
+		}
+	}
 }
 
 fn meets_quota<N: Number>(quota: &N, count_card: &CountCard<N>, opts: &STVOptions) -> bool {
@@ -412,17 +508,19 @@ fn meets_quota<N: Number>(quota: &N, count_card: &CountCard<N>, opts: &STVOption
 }
 
 fn elect_meeting_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions) {
-	let quota = &state.quota; // Have to do this or else the borrow checker gets confused
-	let mut cands_meeting_quota: Vec<(&&Candidate, &mut CountCard<N>)> = state.candidates.iter_mut()
-		.filter(|(_, cc)| cc.state == CandidateState::HOPEFUL && meets_quota(quota, cc, opts))
+	let vote_req = state.vote_required_election.as_ref().unwrap(); // Have to do this or else the borrow checker gets confused
+	
+	let mut cands_meeting_quota: Vec<&Candidate> = state.election.candidates.iter()
+		.filter(|c| { let cc = state.candidates.get(c).unwrap(); cc.state == CandidateState::HOPEFUL && meets_quota(vote_req, cc, opts) })
 		.collect();
 	
 	if cands_meeting_quota.len() > 0 {
 		// Sort by votes
-		cands_meeting_quota.sort_unstable_by(|a, b| a.1.votes.partial_cmp(&b.1.votes).unwrap());
+		cands_meeting_quota.sort_unstable_by(|a, b| state.candidates.get(a).unwrap().votes.partial_cmp(&state.candidates.get(b).unwrap().votes).unwrap());
 		
 		// Declare elected in descending order of votes
-		for (candidate, count_card) in cands_meeting_quota.into_iter().rev() {
+		for candidate in cands_meeting_quota.into_iter().rev() {
+			let count_card = state.candidates.get_mut(candidate).unwrap();
 			count_card.state = CandidateState::ELECTED;
 			state.num_elected += 1;
 			count_card.order_elected = state.num_elected as isize;
@@ -431,6 +529,16 @@ fn elect_meeting_quota<N: Number>(state: &mut CountState<N>, opts: &STVOptions)
 				"{} meet the quota and are elected.",
 				vec![&candidate.name]
 			);
+			
+			if opts.quota_mode == QuotaMode::ERS97 {
+				// Vote required for election may have changed
+				calculate_quota(state, opts);
+			}
+		}
+		
+		if opts.quota_mode == QuotaMode::ERS97 {
+			// Repeat in case vote required for election has changed
+			elect_meeting_quota(state, opts);
 		}
 	}
 }
@@ -440,8 +548,9 @@ where
 	for<'r> &'r N: ops::Sub<&'r N, Output=N>,
 	for<'r> &'r N: ops::Neg<Output=N>
 {
+	let quota = state.quota.as_ref().unwrap();
 	let mut has_surplus: Vec<(&&Candidate, &CountCard<N>)> = state.candidates.iter()
-		.filter(|(_, cc)| cc.votes > state.quota)
+		.filter(|(_, cc)| &cc.votes > quota)
 		.collect();
 	
 	if has_surplus.len() > 0 {
@@ -538,7 +647,7 @@ where
 	for<'r> &'r N: ops::Neg<Output=N>
 {
 	let count_card = state.candidates.get(elected_candidate).unwrap();
-	let surplus = &count_card.votes - &state.quota;
+	let surplus = &count_card.votes - state.quota.as_ref().unwrap();
 	
 	let votes;
 	match opts.surplus {
@@ -633,7 +742,7 @@ where
 	// Finalise candidate votes
 	let count_card = state.candidates.get_mut(elected_candidate).unwrap();
 	count_card.transfers = -&surplus;
-	count_card.votes.assign(&state.quota);
+	count_card.votes.assign(state.quota.as_ref().unwrap());
 	checksum -= surplus;
 	
 	// Update loss by fraction
diff --git a/src/stv/wasm.rs b/src/stv/wasm.rs
index 5098b49..475187f 100644
--- a/src/stv/wasm.rs
+++ b/src/stv/wasm.rs
@@ -63,8 +63,8 @@ macro_rules! impl_type {
 		
 		#[wasm_bindgen]
 		#[allow(non_snake_case)]
-		pub fn [<init_results_table_$type>](election: &[<Election$type>]) -> String {
-			return init_results_table(&election.0);
+		pub fn [<init_results_table_$type>](election: &[<Election$type>], opts: &stv::STVOptions) -> String {
+			return init_results_table(&election.0, opts);
 		}
 		
 		#[wasm_bindgen]
@@ -132,12 +132,15 @@ impl_type!(Rational);
 
 // Reporting
 
-fn init_results_table<N: Number>(election: &Election<N>) -> String {
+fn init_results_table<N: Number>(election: &Election<N>, opts: &stv::STVOptions) -> String {
 	let mut result = String::from(r#"<tr class="stage-no"><td rowspan="3"></td></tr><tr class="stage-kind"></tr><tr class="stage-comment"></tr>"#);
 	for candidate in election.candidates.iter() {
 		result.push_str(&format!(r#"<tr class="candidate transfers"><td rowspan="2">{}</td></tr><tr class="candidate votes"></tr>"#, candidate.name));
 	}
 	result.push_str(r#"<tr class="info transfers"><td rowspan="2">Exhausted</td></tr><tr class="info votes"></tr><tr class="info transfers"><td rowspan="2">Loss by fraction</td></tr><tr class="info votes"></tr><tr class="info transfers"><td>Total</td></tr><tr class="info transfers"><td>Quota</td></tr>"#);
+	if opts.quota_mode == stv::QuotaMode::ERS97 {
+		result.push_str(r#"<tr class="info transfers"><td>Vote required for election</td></tr>"#);
+	}
 	return result;
 }
 
@@ -145,7 +148,7 @@ fn describe_count<N: Number>(filename: String, election: &Election<N>, opts: &st
 	let mut result = String::from("<p>Count computed by OpenTally (revision ");
 	result.push_str(crate::VERSION);
 	let total_ballots = election.ballots.iter().fold(N::zero(), |acc, b| { acc + &b.orig_value });
-	result.push_str(&format!(r#"). Read {:.dps$} ballots from &lsquo;{}&rsquo; for election &lsquo;{}&rsquo;. There are {} candidates for {} vacancies. Counting using options <span style="font-family: monospace;">{}</span>.</p>"#, total_ballots, filename, election.name, election.candidates.len(), election.seats, opts.describe::<N>(), dps=opts.pp_decimals));
+	result.push_str(&format!(r#"). Read {:.0} ballots from &lsquo;{}&rsquo; for election &lsquo;{}&rsquo;. There are {} candidates for {} vacancies. Counting using options <span style="font-family: monospace;">{}</span>.</p>"#, total_ballots, filename, election.name, election.candidates.len(), election.seats, opts.describe::<N>()));
 	return result;
 }
 
@@ -182,7 +185,10 @@ fn update_results_table<N: Number>(stage_num: usize, state: &CountState<N>, opts
 	total_vote += &state.loss_fraction.votes;
 	result.push(&format!(r#"<td class="count">{}</td>"#, pp(&total_vote, opts.pp_decimals)).into());
 	
-	result.push(&format!(r#"<td class="count">{}</td>"#, pp(&state.quota, opts.pp_decimals)).into());
+	result.push(&format!(r#"<td class="count">{}</td>"#, pp(state.quota.as_ref().unwrap(), opts.pp_decimals)).into());
+	if opts.quota_mode == stv::QuotaMode::ERS97 {
+		result.push(&format!(r#"<td class="count">{}</td>"#, pp(state.vote_required_election.as_ref().unwrap(), opts.pp_decimals)).into());
+	}
 	
 	return result;
 }
diff --git a/tests/aec.rs b/tests/aec.rs
index 9e5a903..3226669 100644
--- a/tests/aec.rs
+++ b/tests/aec.rs
@@ -61,6 +61,7 @@ fn aec_tas19_rational() {
 		round_quota: Some(0),
 		quota: stv::QuotaType::Droop,
 		quota_criterion: stv::QuotaCriterion::GreaterOrEqual,
+		quota_mode: stv::QuotaMode::Static,
 		surplus: stv::SurplusMethod::UIG,
 		surplus_order: stv::SurplusOrder::ByOrder,
 		transferable_only: false,
diff --git a/tests/prsa.rs b/tests/prsa.rs
index 9d30fca..63594e5 100644
--- a/tests/prsa.rs
+++ b/tests/prsa.rs
@@ -29,6 +29,7 @@ fn prsa1_rational() {
 		round_quota: Some(3),
 		quota: stv::QuotaType::Droop,
 		quota_criterion: stv::QuotaCriterion::GreaterOrEqual,
+		quota_mode: stv::QuotaMode::Static,
 		surplus: stv::SurplusMethod::EG,
 		surplus_order: stv::SurplusOrder::ByOrder,
 		transferable_only: true,